* Use serviceerror.Unavailable error type instead of serviceerror.Internal
* serviceerror.Unavailable indicates errors like service's dependency is down, retryable
* serviceerror.Internal indicates errors like NPE in service logic, non-retryable
* Try using a set of default database names when initializing admin connection
Aiven DB is a PostgreSQL compatible DB, but comes with a different default DB name
* Add version check method to SQL interface
* Remove tools version check method in favor of functions defined in persistence package
* Refactor tests to not depend on tools package