Added new Couchbase Driver

[Ahbrown41]

Add a new database driver for Couchbase Server supporting:

• N1QL-based migrations via JSON migration files
• Scope-level migrations with configurable collections
• Advisory locking via document-based locks
• Connection via URL or programmatic instance

Includes local fork of dktest with two fixes needed for
Docker-based integration tests:

• Use API version negotiation instead of hardcoded v1.41
• Handle IPv6 wildcard (::) in port bindings
• Added fixes to get dktest working with Couchbase dhui/dktest#48
• I did see this note (DOCKER_API_VERSION), so ignore if not needed.

Tested against couchbase:community-7.6.2 and community-8.0.0.

[Copilot]

Pull request overview

Adds a new Couchbase database driver to migrate/v4, intended to support N1QL-based JSON migrations, scope/collection configuration, and advisory locking, plus CLI build-tag wiring and integration tests.

Changes:

• Introduces database/couchbase driver implementation with URL parsing, migration execution, versioning, and locking.
• Adds Couchbase docker-based integration tests and example JSON migration files.
• Wires Couchbase into CLI build tags and Makefile, and updates go.mod/go.sum (including a local dktest replace).

Reviewed changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
internal/cli/build_couchbase.go	Adds build-tagged blank import to include Couchbase driver in CLI builds.
database/couchbase/couchbase.go	New Couchbase driver implementation (Open/Run/Lock/Version/Drop/etc.).
database/couchbase/couchbase_test.go	Adds docker-based integration tests for Couchbase 7.6.2 and 8.0.0.
database/couchbase/examples/migrations/*.json	Adds example N1QL JSON migration files.
Makefile	Adds couchbase to the DATABASE build tag list.
go.mod	Updates Go version/deps and adds replace github.com/dhui/dktest => ./_dktest_local.
go.sum	Adds checksums for newly introduced/upgraded dependencies.

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[coveralls]

coverage: 55.105% (+0.7%) from 54.432% — Ahbrown41:feature/add-couchbase-driver into golang-migrate:master

[Ahbrown41]

Hey @dhui let me know if I can help clarify anything with this PR or improve it. It is a great project, happy to help with some of the support to make it even better. I have some thoughts on testing etc that is worth a convo.

[Ahbrown41]

@joschi happy to help here, let me know if anything is needed. I see you adjusted the contexts, oops I could have done that. Any idea if when this might see the light of day?