fix(outbox-store): guard against empty statuses at OoutboxStore.findOldestCreatedAt()

[rawo]

#60

Fixed issue #60 on branch bugfix/issue-60: findOldestCreatedAt built WHERE status IN () when passed an empty statuses set — a SQL syntax error on both Postgres and MySQL.

Fix: added if (statuses.isEmpty()) return emptyMap() as an early guard in both PostgresOutboxStore.findOldestCreatedAt and MysqlOutboxStore.findOldestCreatedAt. This is the semantically correct result (not an error) — an empty statuses set trivially matches nothing, consistent with the existing "statuses with no entries are omitted from the result" contract.

Docs: updated the OutboxStore.findOldestCreatedAt KDoc to state that an empty statuses set returns an empty map.

Tests: added one regression test to the shared outboxStoreContractTests suite (okapi-integration-tests), which runs automatically against both real Postgres and MySQL via Testcontainers — no per-adapter duplication needed.

Verified against a regression: reverted just the two main-code fixes via git stash, reran the suite — both new tests failed with real SQLSyntaxErrorException/PSQLException as predicted, all 20 other tests still passed. Restored the fix; full run is green again (22/22).

ktlintCheck clean across okapi-postgres, okapi-mysql, okapi-core, okapi-integration-tests.

[Copilot]

Pull request overview

Fixes a SQL syntax error in the JDBC outbox-store adapters when findOldestCreatedAt() is called with an empty statuses set (previously generating WHERE status IN ()). This aligns runtime behavior with the contract that “no matching statuses” yields no results.

Changes:

• Added an early return emptyMap() guard for statuses.isEmpty() in both Postgres and MySQL findOldestCreatedAt() implementations.
• Updated the OutboxStore.findOldestCreatedAt KDoc to document the empty-input behavior.
• Added a contract regression test ensuring empty statuses returns an empty map (and does not error).

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
okapi-postgres/src/main/kotlin/com/softwaremill/okapi/postgres/PostgresOutboxStore.kt	Prevents generating invalid IN () SQL by short-circuiting on empty statuses.
okapi-mysql/src/main/kotlin/com/softwaremill/okapi/mysql/MysqlOutboxStore.kt	Prevents generating invalid IN () SQL by short-circuiting on empty statuses.
okapi-integration-tests/src/test/kotlin/com/softwaremill/okapi/test/store/OutboxStoreContractTests.kt	Adds regression coverage for empty statuses input across adapters.
okapi-core/src/main/kotlin/com/softwaremill/okapi/core/OutboxStore.kt	Documents that empty statuses returns an empty map.

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