(reversible) rename_constraint helper

[ccutrer]

also add constraint_exists?

[Copilot]

Pull request overview

Adds a new rename_constraint migration/helper for PostgreSQL (with optional if_exists: behavior) and makes it reversible through ActiveRecord’s CommandRecorder, integrating the recorder via the gem’s Railtie.

Changes:

• Add PostgreSQLAdapter#rename_constraint that emits ALTER TABLE ... RENAME CONSTRAINT ....
• Add constraint_exists? helper used to implement if_exists: behavior.
• Add ActiveRecord::PGExtensions::CommandRecorder support and wire it into Rails initialization; add specs for the new behavior.

Reviewed changes

Copilot reviewed 5 out of 8 changed files in this pull request and generated 1 comment.

File	Description
spec/postgresql_adapter_spec.rb	Adds specs for SQL emitted by rename_constraint, if_exists: behavior (stubbed), and reversibility via CommandRecorder.
lib/active_record/pg_extensions/railtie.rb	Loads the new command recorder extension and includes it into ActiveRecord::Migration::CommandRecorder.
lib/active_record/pg_extensions/postgresql_adapter.rb	Introduces rename_constraint and constraint_exists? used to support if_exists:.
lib/active_record/pg_extensions/command_recorder.rb	Adds recording + inversion logic so rename_constraint is reversible in migrations.

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