[dagster-iceberg] support `dg.EnvVar` in `IcebergCatalogConfig`

[cmpadden]

A user reported on Reddit that they were unable to use EnvVar nested within the Icerberg catalog configuration.

defs = Definitions(
    assets=[breaks_files],
    resources={
        'iceberg_io_manager': PyArrowIcebergIOManager(
            name="default",
            config=IcebergCatalogConfig(
                properties={
                    "type": "hive",
                    "uri": EnvVar('HIVE_METASTORE_URI'),
                    "warehouse": EnvVar('HOT_STORAGE_ENDPOINT_URL'),
                    "s3.access_key_id": EnvVar('S3_ACCESS_KEY_ID_ICEBERG'),
                    "s3.secret_access_key": EnvVar('S3_SECRET_ACCESS_KEY_ICEBERG'),
                }
            ),
            namespace="default",
        ),
    }
)

@JasperHG90 , are you familiar with any limitations in the configuration properties in this regard? Thanks.

[stevenayers]

I'm not sure if this is still oustanding, but I think you might need to use dg.ConfigurableResource for IcebergCatalogConfig, similar to the PowerBI integration:

from dagster_powerbi import (
    PowerBIServicePrincipal,
    PowerBIToken,
    PowerBIWorkspace,
    load_powerbi_asset_specs,
)

import dagster as dg

# Connect using a service principal
power_bi_workspace = PowerBIWorkspace(  # <--- a dg.ConfigurableResource
    credentials=PowerBIServicePrincipal(  # <--- also a dg.ConfigurableResource
        client_id=dg.EnvVar("POWER_BI_CLIENT_ID"),
        client_secret=dg.EnvVar("POWER_BI_CLIENT_SECRET"),
        tenant_id=dg.EnvVar("POWER_BI_TENANT_ID"),
    ),
    workspace_id=dg.EnvVar("POWER_BI_WORKSPACE_ID"),
)