Destinations: destination-gcs-data-lake - Make Apache Polaris Realm Configurable (Polaris-Realm Header)

[vai-airbyte]

Describe the feature request
Customers using Apache Polaris in multi-realm deployments cannot connect to their Polaris catalog because the Polaris-Realm HTTP header is not configurable. The connectors currently assume a single-realm deployment (default realm: POLARIS).
As a result, connection attempts fail with a “Missing or invalid realm” error when a non-default realm is required.

Describe the solution you'd like
Add an optional realm field to the Polaris catalog configuration. When provided, this value should be sent as the Polaris-Realm HTTP header in all requests to the Polaris catalog.
If the field is not set, the connector should continue using the default behavior to preserve backward compatibility.

Describe alternatives you've considered
Requiring customers to restructure their Polaris deployments to use a single realm, which is not practical or aligned with Polaris’ multi-realm design.

Hardcoding additional realm values, which does not scale and still limits configurability.

Additional context
Apache Polaris supports multi-realm deployments to isolate catalogs, principals, and access controls. In these setups, the Polaris-Realm header is required for API requests to succeed. Without exposing this as a configuration option, multi-realm Polaris environments cannot be used with these connectors.