Postgres CDC connector: follow-up fixes and improvements (tracking) #6126

Context

Tracking issue for follow-up work on the Postgres CDC input connector (landed in #5988). Collects the smaller fixes and improvements from PR review that were deferred.

Items that need discussion have their own separate issues.

Checklist

Small fixes (clear, ~minutes each)

• PgNumeric NaN/Infinity → Value::Null in cell_to_json and array_cell_to_json
• Require schema-qualified table matching in FelderaDestination::is_target_table; default to public. when unqualified
• Add tracing::warn! when write_table_rows falls back to col_0, col_1, ... due to missing relation info
• Add unit test for nanosecond-precision timestamp round-trip (%.f suppresses trailing zeros)
• Add // NOTE: comment near Resume::Seek construction explaining identity-vs-position semantics
• Document that PostgresStore creates an etl.* schema on the source DB in PostgresCdcReaderConfig docstring

Real bug

• Wire PostgresCdcReaderConfig::tls through to etl's TlsConfig. Currently parse_pg_uri hardcodes TlsConfig::disabled(), so the tls config field is silently ignored.

Config/validation

• Validate uri, publication, source_table at config parse time (fail at deploy, not pipeline start)
• Document duplicate-deployment limitation: two Feldera pipelines against the same (uri, publication, source_table) would compute the same pipeline_id and collide on the replication slot

Testing

• Failover integration test using the full Feldera controller: insert → kill mid-batch → restart → verify no data loss/duplication
• Integration tests for edge cases:
  • Schema changes mid-stream
  • Large transactions (thousands of rows in single tx, 2MB buffer splitting)
  • Multiple tables in publication (verify source_table filtering)
  • TRUNCATE events (currently logged and ignored — verify no crash)
  • Empty table snapshot (zero rows, then streaming starts)
  • REPLICA IDENTITY without FULL (updates/deletes without old row)
  • Rapid insert/update/delete cycles on the same row
  • Connection loss / Postgres restart mid-stream
  • Slot invalidation (slot dropped externally)
  • Long-running transactions
  • Special float values (NaN, Infinity) through the full pipeline

Documentation

• User-facing connector documentation page under docs.feldera.com/docs/connectors/sources/ covering setup, privileges, config, limitations, known issues