feat(alembic): auto-enable PostgreSQL enum migration detection

[hasansezertasan]

Summary

Closes #492.

Alembic's autogenerate cannot detect changes to PostgreSQL native ENUM types on its own (for example, adding a value to an existing StrEnum). Those changes are silently skipped, leaving the schema out of sync. The established fix is the alembic-postgresql-enum package, which registers the missing autogenerate comparators purely as an import side effect.

Since Advanced Alchemy ships its own migration env.py templates, this PR wires that support in directly so it works out of the box.

Changes

• alembic/templates/{sync,asyncio}/env.py — Guarded import alembic_postgresql_enum in a try/except ImportError. It activates only when the package is installed and is a no-op otherwise, so no existing users break.
• pyproject.toml — New public postgresql extra (pip install "advanced-alchemy[postgresql]") and the package added to the dev postgres group so CI exercises it.
• docs/usage/cli.rst — Documents the behavior under make-migrations, including how existing projects can enable it by adding the import to an already-generated env.py.
• tests/integration/test_alembic_commands.py — Asserts the generated env.py includes the conditional import.

Notes

The generated template intentionally keeps an explicit try/except (rather than contextlib.suppress) since users read and edit these files; SIM105 is ignored for the template path accordingly.

🤖 Generated with Claude Code

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📚 Documentation preview: https://litestar-org.github.io/advanced-alchemy-docs-preview/774

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.45%. Comparing base (8dc8285) to head (31be229).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #774      +/-   ##
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+ Coverage   82.43%   82.45%   +0.02%     
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  Files         105      105              
  Lines        9039     9039              
  Branches     1219     1219              
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+ Hits         7451     7453       +2     
+ Misses       1262     1260       -2     
  Partials      326      326              

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[Copilot]

Pull request overview

This PR updates Advanced Alchemy’s Alembic env.py templates to automatically opt into PostgreSQL native ENUM autogenerate support (via alembic-postgresql-enum) when the optional dependency is installed, addressing enum-value additions not being detected during migration generation.

Changes:

• Add a guarded import of alembic_postgresql_enum to the sync and asyncio Alembic env.py templates to enable enum diff detection via import side effects.
• Introduce a new public postgresql optional extra and update lock/dev dependency groups so CI/dev can exercise the integration.
• Document the behavior in CLI docs and add an integration test asserting the generated env.py contains the conditional import.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
advanced_alchemy/alembic/templates/sync/env.py	Adds conditional import to enable PostgreSQL enum autogenerate support in sync migrations.
advanced_alchemy/alembic/templates/asyncio/env.py	Adds conditional import to enable PostgreSQL enum autogenerate support in asyncio migrations.
pyproject.toml	Adds postgresql extra and updates ruff per-file ignores for template style.
uv.lock	Locks alembic-postgresql-enum and exposes the new extra in lock metadata/groups.
docs/usage/cli.rst	Documents the new enum detection behavior and installation path.
tests/integration/test_alembic_commands.py	Adds a test to ensure generated env.py includes the conditional import.

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[cofin]

I'll take a review of this tonight. I think we have to be careful to ensure this is not a breaking change for the 1.0 branch. This would include the migrations scaffolding as well, which I think is the challenge.