Tango V04 migration stores token response metadata and authorization completion mode.

Existing sessions and candidates default to connection completion. Consume mode forbids connection bindings. This revision retains schema version 4 under the no-external-consumers migration exception. An already-applied V04 requires an explicit schema-shape check and targeted reconciliation to retain data, or fresh recreation of a disposable developer database. The version marker alone is insufficient. This revised down migration queries completion_mode and cannot run on the original V04 schema without those columns; do not use the current wrapper to roundtrip that schema.

Rollback takes ACCESS EXCLUSIVE locks on sessions, then authorizations, held through migration completion. Before DDL it refuses unexpired consume sessions not yet exchanged and unexpired, unconsumed consume candidates. Complete or expire pending work and use normal cleanup before retrying. See the setup and upgrading guides for deployment and rollback requirements.