Add PostgreSQL Metadata Provider for DuckLake Catalogs #8
Description
Description
Add PostgreSQL as a supported catalog metadata backend for DataFusion–DuckLake alongside the existing DuckDB implementation. This introduces a PostgresMetadataProvider that implements the existing MetadataProvider trait and reuses the same database-agnostic SQL queries. The change enables DataFusion–DuckLake deployments backed by managed PostgreSQL services such as Amazon RDS or Cloud SQL, while preserving the current behavior and APIs.
Current Behavior
Catalog metadata is only supported via DuckDB using DuckdbMetadataProvider.
New Behavior
Introduce PostgresMetadataProvider, allowing catalog metadata to be stored and queried from PostgreSQL