Deduplicate DatabaseJanitor codebase after async introduction

[tboy1337]

Follow-up refactor after #1295 introduced AsyncDatabaseJanitor alongside the existing sync DatabaseJanitor.

This PR consolidates shared janitor logic into a new BaseDatabaseJanitor base class:

• Shared __init__ with version parsing and configuration assignment
• Shared is_template() implementation
• Shared _build_create_database_sql() for CREATE DATABASE DDL construction
• Class-level type annotations preserved on the base class

DatabaseJanitor and AsyncDatabaseJanitor now inherit from BaseDatabaseJanitor, removing the _JanitorConfig dataclass, _JanitorConfigTarget protocol, and related helper functions (_init_janitor_config, _apply_janitor_config, module-level _build_create_database_sql).

Sync/async-specific methods (init, drop, cursor, load, and connection helpers) remain in their respective subclasses, since they require separate sync and async implementations.

This builds on the intent of #1364 and closes the remaining small deduplication gap by hoisting is_template() into the base class and keeping explicit type annotations.

Changes

• pytest_postgresql/janitor.py — introduce BaseDatabaseJanitor; slim down sync/async subclasses
• newsfragments/+dedupe-janitor.misc.rst — changelog entry

No public API changes: DatabaseJanitor and AsyncDatabaseJanitor constructors and behavior are unchanged.

Summary by CodeRabbit

• Refactor
  • Improved consistency between synchronous and asynchronous database janitor operations.
  • Centralised shared database configuration and database creation logic for more predictable behaviour.
  • Streamlined template handling and database SQL generation across both modes.
• Documentation
  • Added a release note documenting deduplication following the introduction of asynchronous support.

[coderabbitai]

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between dfb3bf2 and ed34e6d.

📒 Files selected for processing (1)

• pytest_postgresql/janitor.py

🚧 Files skipped from review as they are similar to previous changes (1)

• pytest_postgresql/janitor.py

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📝 Walkthrough

Walkthrough

The refactor adds BaseDatabaseJanitor to centralise janitor configuration, version parsing, template detection, and CREATE DATABASE SQL generation. Synchronous and asynchronous janitors inherit this shared behaviour and use the instance SQL builder.

Changes

DatabaseJanitor deduplication

Layer / File(s)	Summary
Shared janitor configuration and SQL builder pytest_postgresql/janitor.py	Adds BaseDatabaseJanitor, storing configuration on the instance and providing shared template detection and CREATE DATABASE SQL construction.
Synchronous and asynchronous integration pytest_postgresql/janitor.py, newsfragments/*	Updates both janitor implementations to use the shared SQL builder and template predicate, and records the deduplication in a newsfragment.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• dbfixtures/pytest-postgresql#1364: Introduces the same BaseDatabaseJanitor deduplication refactor and shared SQL-building logic.

🚥 Pre-merge checks | ✅ 6

✅ Passed checks (6 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main refactor: deduplicating DatabaseJanitor and AsyncDatabaseJanitor after the async introduction.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Newsfragment Check	✅ Passed	PASS: newsfragments/+dedupe-janitor.misc.rst is present, and pyproject.toml lists 'misc' as a valid towncrier fragment type.

✨ Finishing Touches

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• Create PR with unit tests

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✅ All modified and coverable lines are covered by tests.

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[tboy1337]

@fizyk