* refactor: ensure sequencers are unique
Adds a unique constraint to ensure only one sequencer record exists for
each Kafka (topic, partition).
* test: use DSN from env for integration tests
Removes the hard-coded DSN, instead sourcing it from the DATABASE_URL
environment variable.
* docs: integration testing for iox_catalog
Documents the required steps in order to run the Postgres integration
tests for the iox_catalog crate.
* feat(iox_catalog): create & list sequencers
Adds support for interacting with the "sequencer" table.
* chore: update lockfile
Running cargo in iox_catalog generates a lockfile diff.
Ryan Russell
Carol (Nichols || Goulding)
Marko Mikulicic
Marco Neumann
Dom
Paul Dix