Immutable Classes: New Database Columns immutable_json and immutable_hash

I split branch 547-immutable-datenfelder (!423 (closed)) into more manageable PRs.

This one builds up on !435 (merged).

• Add database columns immutable_json and immutable_hash for schema and three other resources
• Write into new columns on import
• No backfill script, yet

Work on the backfill script continues in branch backfill-immutable-columns https://gitlab.opencode.de/fitko/fim/schema-repository/-/compare/main...backfill-immutable-columns?from_project_id=1010&straight=false