Marcin Figiel

### Issue description Micronaut uses a [custom media type](https://github.com/micronaut-projects/micronaut-core/issues) for YAML: `application/x-yaml`, while IANA [recently registered](https://www.rfc-editor.org/rfc/rfc9512.html) an official `application/yaml`. Micronaut should adopt this official type in its codebase.

### Expected Behavior When running multiple concurrent DB operations with few transactions each, all of them should end succesfully eventually. ### Actual Behaviour Transactions fail randomly. ### Steps To Reproduce...