refactor(api): remove MongoDB store, keep Postgres as sole implementation

[otavio]

What

Removes the entire MongoDB store implementation and the one-time Mongo→Postgres data-migration tool, leaving the store.Store interface in place with PostgreSQL as the only implementation.

⚠️ Merge in lockstep with the cloud PR

This must merge together with the companion PR in shellhub-io/cloud (branch feat/remove-mongodb-store). Cloud builds against this repo via replace => ../shellhub and imports the now-deleted api/store/mongo and api/store/migrate packages. Merging this alone breaks cloud main/CI until the cloud PR lands. Coordinate the merges.

Why

The Mongo→Postgres migration is finalized; the MongoDB backend and its migration code are dead weight. The interface abstraction is intentionally preserved so a future backend remains possible.

Changes

• store: deleted api/store/mongo/ (impl + 119 migrations), api/store/migrate/ (incl. RegisterMigrationExtension), storetest/mongoprovider/, and api/pkg/dbtest/. Kept the store.Store interface, mocks, the generic storetest harness, RegisterStoreWrapper, and pg/internal legacyMongoFieldMapping.
• wiring: api server and cli construct the pg store unconditionally. Dropped the DATABASE switch, the migrate mode (and its unauthenticated GET /api/migration/status listener), and MONGO_URI. The cli keeps its existing pg options and does not run migrations.
• errors: added store.ErrInternal (unique error code). pg.fromSQLError wraps unmapped errors with it so the echo handler keeps reporting unknown DB errors to Sentry as 500s; context.Canceled/DeadlineExceeded pass through unwrapped to avoid alert noise. Removed the dead mongo.ErrUserNotFound branch in removeMember — absent members are already caught by the FindMember precheck.
• deps: go mod tidy dropped mongo-driver, mongotest, mongo-lock, mongo-migrate, and the mongodb testcontainers module; modules/postgres retained.
• infra/ci: removed docker-compose.mongo*.yml, the mongo leg of bin/docker-compose, MONGO_URI from the enterprise compose, and the database: mongo qa matrix entry (postgres leg kept).

Testing

• go build ./... and go vet ./... clean in api/ and cli/.
• New unit tests cover: fromSQLError wrapping vs. context-error passthrough; the handler reporting ErrInternal (and not reporting ErrNoDocuments/context.Canceled); and the removeMember precheck path.
• The pg storetest suite (proof the pg store still satisfies the full interface) passes in the dev stack.

Follow-up

The docs repo upgrade guide (self-hosted/upgrading.md) still references the removed GET /api/migration/status endpoint — separate docs PR.

[github-actions]

Claude finished @otavio's task in 6m 23s —— View job

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Code Review Complete

Reviewed 23 modified/added files across code quality, security, testing, Go patterns, and architecture — no issues found. The code looks good as-is.

Review highlights:

• Error handling: fromSQLError correctly wraps unmapped errors with store.ErrInternal while passing through context.Canceled/DeadlineExceeded. The error handler's ErrInternal → Sentry + 500 path works correctly with errors.Join.
• Dead code removal: The mongo.ErrUserNotFound branch in removeMember was indeed dead — the FindMember precheck on line 155 already catches absent members before removeMember is called.
• Cross-repo compatibility: Cloud's feat/remove-mongodb-store branch has no remaining imports of deleted packages (api/store/mongo, api/store/migrate, api/pkg/dbtest). store.Store interface is preserved. No breaking changes detected.
• Test coverage: New tests cover fromSQLError wrapping, context-error passthrough, the error handler's Sentry reporting, removeMember error propagation, and cleanup guard tests that assert mongo dirs/deps are gone.
• Security: Removing the unauthenticated GET /api/migration/status endpoint reduces attack surface. No new vulnerabilities introduced.

To request another review round, comment /review.