Requesting the GML application schema of a collection with HTTP schema references results in an error

[julianzz98]

Describe the bug

Requesting the GML application schema of a collection that uses HTTP schema references results in a 500 Internal Server Error.

The request:

curl -X 'GET' \
  'http://localhost:8182/deegree-ogcapi/datasets/BoreholeML_3.1.0/collections/Borehole/appschema' \
  -H 'accept: application/xml'

creates the following output in the logs:

deegree-ogcapi-1  | 2025-10-30 18:24:10,138 ERROR o.d.s.o.s.SchemaResponseGmlWriter [http-nio-8080-exec-1] Schema could not be written
deegree-ogcapi-1  | java.nio.file.FileSystemNotFoundException: Provider "https" not installed
[...]
deegree-ogcapi-1  | javax.xml.stream.XMLStreamException: Trying to write END_DOCUMENT when document has no root (ie. trying to output empty document).
[...]

The issue likely occurs because the schema in the SQLFeatureStore configuration is provided via an HTTP reference, even though the system expects the schema to be available as a local file on the filesystem.

To Reproduce

• Configure a SQLFeatureStore with a schema referenced via HTTP
• Deploy/start the service
• Request the GML application schema of the affected collection (e.g. cURL)
• Observe the 500 Internal Server Error in the deegree-ogcapi logs

Expected behavior

The GML application schema should be returned without errors, or the system should be able to handle HTTP-based schema references.

Additional context

• Version: 1.3.x and 2.0.x
• Datasource: Postgres/PostGIS, MS SQL Server, Orac
• While providing the schema as a local file on the filesystem, the request works as expected