[Integration] Publish physical schema observations for OpenMetadata interoperability

[seonghobae]

Buyer problem

Customers need PostgreSQL and supported warehouse schemas observed by pg-erd-cloud to become governed metadata without manually recreating tables, columns, constraints, and schema revisions in OpenMetadata.

Boundary

• pg-erd-cloud owns physical schema inspection, snapshots, diff, ERD, and migration evidence.
• It emits provider-neutral observed metadata/evidence through a released context-graph-contracts contract.
• semantic-data-portal admits and projects that evidence and owns the OpenMetadata anti-corruption/write boundary.
• pg-erd-cloud must not embed an OpenMetadata SDK, store OpenMetadata credentials, write directly to OpenMetadata, or query SDP databases.

Scope

• Produce a versioned physical-schema observation envelope for database, schema, table, column, key, constraint, index, view, and supported relation identities.
• Preserve source engine, normalized connection identity without credentials, snapshot ID/hash, inspector version, captured time, and database-native identifiers.
• Publish schema additions, removals, and modifications as explicit snapshot/diff evidence.
• Represent physical lineage only where deterministically observed; do not infer business lineage.
• Emit no sample rows, credential material, DSNs, unbounded DDL, or query text in the general event.
• Provide an operation receipt so SDP can reconcile every admitted or rejected observation.
• Add an end-to-end fixture: PostgreSQL schema → pg-erd snapshot → contract event → SDP projection → OpenMetadata-ready table/column representation.

Acceptance

• Same snapshot event is replay-idempotent.
• Snapshot and diff hashes are deterministic for equivalent physical schemas.
• Dropped objects close validity rather than deleting historical observations.
• Unknown ownership, glossary, quality, and business domain remain unknown; pg-erd-cloud does not invent them.
• Cross-tenant and cross-connection identity collisions are rejected.
• Production statement/branch coverage and public API docs: 100%.
• Real PostgreSQL integration, migration, fuzz, credential-redaction, and large-schema tests.

Dependency order

1. context-graph-contracts#26 released.
2. SDP durable admission contract released from semantic-data-portal#95.
3. Producer implementation and exact-version consumer E2E.

Related: ContextualWisdomLab/semantic-data-portal#95, ContextualWisdomLab/context-graph-contracts#26.