Core interfaces, dispatcher, poller, and registries for the outbox pattern framework

JDBC persistence for the outbox pattern framework (H2, MySQL, PostgreSQL)

Micrometer metrics bridge for the outbox pattern framework

Spring transaction integration for the outbox pattern framework

Gson-based JsonCodec SPI implementation for the outbox framework

Spring Boot auto-configuration for the outbox pattern framework

Test fixtures and stubs for unit testing code that uses the outbox framework