fix(review): support clearing chat_webhook_url via empty string

- Remove dsl.Format(dsl.FormatURI) from ChatWebhookURLAttribute so that
  an empty string passes Goa validation (FormatURI rejected "")
- Change httpsURLPattern to ^$|^https://... to allow the empty-string
  clear signal while still requiring HTTPS for actual URLs
- Update preserve/clear guard in UpdateSettings: nil/absent preserves
  the existing URL (safe for GET→PUT round-trips); "" explicitly clears
  it (sets stored value to nil); a non-empty URL replaces it
- Add comments on all three sanitization sites (create indexer, update
  indexer, NATS event old/new snapshots)
- Add TestCommitteeWriterOrchestrator_UpdateSettings_ChatWebhookURLSemantics
  covering omit-preserves, empty-string-clears, replace, and nil-stored cases

LFXV2-3094

Generated with [Claude Code](https://claude.ai/code)

Signed-off-by: Andres Tobon <andrest2455@gmail.com>

Author: andrest50

cmd/committee-api/design/type.go

@@ -208,9 +208,11 @@ func DescriptionAttribute() {
 // would otherwise pass dsl.FormatURI as syntactically valid URIs.
 const urlPattern = `^https?://[^\s/$.?#][^\s]*$`
 
-// httpsURLPattern validates an HTTPS-only URL. Used for fields that carry
-// bearer credentials (e.g. webhook URLs) where plaintext HTTP is unsafe.
-const httpsURLPattern = `^https://[^\s/$.?#][^\s]*$`
+// httpsURLPattern validates an HTTPS-only URL or an empty string.
+// Used for write-only credential fields (e.g. webhook URLs) where:
+//   - a non-empty value must be a valid HTTPS URL (plaintext HTTP is rejected)
+//   - an empty string is the explicit clear signal (see ChatWebhookURLAttribute)
+const httpsURLPattern = `^$|^https://[^\s/$.?#][^\s]*$`
 
 // WebsiteAttribute is the DSL attribute for committee website.
 func WebsiteAttribute() {
@@ -1033,9 +1035,10 @@ func ChatChannelAttribute() {
 }
 
 // ChatWebhookURLAttribute is the DSL attribute for the committee's Slack Incoming Webhook URL.
+// This field is write-only: accepted on create and PUT settings, never returned from GET.
+// Update semantics: omit or send null to preserve the stored URL; send "" to clear it.
 func ChatWebhookURLAttribute() {
-	dsl.Attribute("chat_webhook_url", dsl.String, "Slack Incoming Webhook URL for sharing content to a Slack channel", func() {
-		dsl.Format(dsl.FormatURI)
+	dsl.Attribute("chat_webhook_url", dsl.String, "Slack Incoming Webhook URL for sharing content to a Slack channel. Write-only: never returned from GET. Send empty string to clear a previously stored value; omit the field (or send null) to preserve the existing value.", func() {
 		dsl.Pattern(httpsURLPattern)
 		dsl.MaxLength(500)
 		dsl.Example("https://hooks.slack.example.org/services/TXXXXXXXX/BXXXXXXXX/placeholder")

gen/committee_service/service.go

@@ -4217,10 +4217,9 @@ definitions:
                 maxLength: 500
             chat_webhook_url:
                 type: string
-                description: Slack Incoming Webhook URL for sharing content to a Slack channel
+                description: 'Slack Incoming Webhook URL for sharing content to a Slack channel. Write-only: never returned from GET. Send empty string to clear a previously stored value; omit the field (or send null) to preserve the existing value.'
                 example: https://hooks.slack.example.org/services/TXXXXXXXX/BXXXXXXXX/placeholder
-                format: uri
-                pattern: ^https://[^\s/$.?#][^\s]*$
+                pattern: ^$|^https://[^\s/$.?#][^\s]*$
                 maxLength: 500
             deliverables:
                 type: array
@@ -4978,10 +4977,9 @@ definitions:
                 example: false
             chat_webhook_url:
                 type: string
-                description: Slack Incoming Webhook URL for sharing content to a Slack channel
+                description: 'Slack Incoming Webhook URL for sharing content to a Slack channel. Write-only: never returned from GET. Send empty string to clear a previously stored value; omit the field (or send null) to preserve the existing value.'
                 example: https://hooks.slack.example.org/services/TXXXXXXXX/BXXXXXXXX/placeholder
-                format: uri
-                pattern: ^https://[^\s/$.?#][^\s]*$
+                pattern: ^$|^https://[^\s/$.?#][^\s]*$
                 maxLength: 500
             last_reviewed_at:
                 type: string

gen/http/committee_service/client/cli.go

@@ -6890,10 +6890,9 @@ components:
                     maxLength: 500
                 chat_webhook_url:
                     type: string
-                    description: Slack Incoming Webhook URL for sharing content to a Slack channel
+                    description: 'Slack Incoming Webhook URL for sharing content to a Slack channel. Write-only: never returned from GET. Send empty string to clear a previously stored value; omit the field (or send null) to preserve the existing value.'
                     example: https://hooks.slack.example.org/services/TXXXXXXXX/BXXXXXXXX/placeholder
-                    format: uri
-                    pattern: ^https://[^\s/$.?#][^\s]*$
+                    pattern: ^$|^https://[^\s/$.?#][^\s]*$
                     maxLength: 500
                 deliverables:
                     type: array
@@ -8255,10 +8254,9 @@ components:
                     example: false
                 chat_webhook_url:
                     type: string
-                    description: Slack Incoming Webhook URL for sharing content to a Slack channel
+                    description: 'Slack Incoming Webhook URL for sharing content to a Slack channel. Write-only: never returned from GET. Send empty string to clear a previously stored value; omit the field (or send null) to preserve the existing value.'
                     example: https://hooks.slack.example.org/services/TXXXXXXXX/BXXXXXXXX/placeholder
-                    format: uri
-                    pattern: ^https://[^\s/$.?#][^\s]*$
+                    pattern: ^$|^https://[^\s/$.?#][^\s]*$
                     maxLength: 500
                 last_reviewed_at:
                     type: string

gen/http/committee_service/client/types.go

@@ -526,7 +526,7 @@ func (uc *committeeWriterOrchestrator) Create(ctx context.Context, committee *mo
 
 	if committee.CommitteeSettings != nil {
 		indexSettings := *committee.CommitteeSettings
-		indexSettings.ChatWebhookURL = nil
+		indexSettings.ChatWebhookURL = nil // bearer credential — must not enter the search index
 		settingsMsg, errBuildSettingsMsg := uc.buildIndexerMessage(ctx, model.ActionCreated, &indexSettings, committee.Tags())
 		if errBuildSettingsMsg != nil {
 			return nil, errs.NewUnexpected("failed to build indexer message", errBuildSettingsMsg)
@@ -858,12 +858,13 @@ func (uc *committeeWriterOrchestrator) UpdateSettings(ctx context.Context, setti
 		settings.Auditors = existingSettings.Auditors
 	}
 
-	// Preserve the stored webhook URL when the caller omits the field.
-	// Because chat_webhook_url is write-only (not returned from GET), a
-	// GET→PUT round-trip will always arrive with nil here; overwriting on
-	// every omission would silently wipe the credential on any settings save.
+	// nil (absent/null) → preserve existing; "" → explicit clear; non-empty URL → replace.
+	// Because chat_webhook_url is write-only (not returned from GET), a GET→PUT
+	// round-trip always sends nil — preserve prevents silently wiping the credential.
 	if settings.ChatWebhookURL == nil {
 		settings.ChatWebhookURL = existingSettings.ChatWebhookURL
+	} else if *settings.ChatWebhookURL == "" {
+		settings.ChatWebhookURL = nil
 	}
 
 	// Step 3: Update the committee settings in storage
@@ -894,7 +895,7 @@ func (uc *committeeWriterOrchestrator) UpdateSettings(ctx context.Context, setti
 	committee := &model.Committee{CommitteeBase: *committeeBase, CommitteeSettings: settings}
 	// Build and publish indexer message
 	indexSettings := *settings
-	indexSettings.ChatWebhookURL = nil
+	indexSettings.ChatWebhookURL = nil // bearer credential — must not enter the search index
 	messageIndexer, errBuildIndexerMessage := uc.buildIndexerMessage(ctx, model.ActionUpdated, &indexSettings, committee.Tags())
 	if errBuildIndexerMessage != nil {
 		slog.ErrorContext(ctx, "failed to build indexer message",
@@ -927,9 +928,9 @@ func (uc *committeeWriterOrchestrator) UpdateSettings(ctx context.Context, setti
 	// detect newly added Writers/Auditors and send notification emails.
 	updatedBy, _ := ctx.Value(constants.PrincipalContextID).(string)
 	sanitizedOldSettings := *existingSettings
-	sanitizedOldSettings.ChatWebhookURL = nil
+	sanitizedOldSettings.ChatWebhookURL = nil // bearer credential — must not enter NATS events
 	sanitizedNewSettings := *settings
-	sanitizedNewSettings.ChatWebhookURL = nil
+	sanitizedNewSettings.ChatWebhookURL = nil // bearer credential — must not enter NATS events
 	settingsEvent, errBuildEvent := (&model.CommitteeEvent{}).Build(ctx, model.ResourceCommitteeSettings, model.ActionUpdated, &model.CommitteeSettingsUpdateEventData{
 		CommitteeUID:  settings.UID,
 		OldSettings:   &sanitizedOldSettings,