[soujasK]

Issue number: closes #8659

Summary

Changes

As agreed in #8659 (option 1): BasePersistenceLayer.configure() only applies the config on its first call, so functions sharing a persistence layer instance silently use the first function's IdempotencyConfig. It now remembers the settings it applied and emits a PowertoolsUserWarning when it's configured again with a config whose settings differ, pointing to one persistence layer per config.

• The comparison is on the settings the layer applies (event_key_jmespath, payload_validation_jmespath, jmespath_options, raise_on_no_idempotency_key, expires_after_seconds, use_local_cache, local_cache_max_items, hash_function), not on object identity, so @idempotent without a config (which creates a new IdempotencyConfig() per invocation) doesn't warn. lambda_context and response_hook aren't part of it since they're read per call.
• Behaviour is otherwise unchanged: the first config still wins.
• Docs: a warning admonition below the IdempotencyConfig options table.

Tests: one for the differing-config case (warns, first config's settings kept; fails without the change) and one checking that a new config with the same settings doesn't warn. tests/unit, tests/functional/idempotency and tests/functional/batch pass on Linux (Python 3.12), plus ruff, mypy, ty, bandit and xenon. The existing idempotency tests also pass with this warning turned into an error, so none of them reconfigure a layer with a different config.

User experience

Before: two idempotent functions sharing a persistence layer with different configs silently use the first function's settings, and can return another request's stored response.

After: the same setup emits a PowertoolsUserWarning telling you to use a separate persistence layer instance for each IdempotencyConfig.

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[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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