In RelationalBaseSourceConnector#validate (used as Connector#validate() for relational datastore connectors) we call RelationalBaseSourceConnector#validateConnection when only some connection related config options (like hostname etc) are valid. This can lead to exceptions.
For example when you provide a `schema.include.list` for a Postgres connector with an invalid regular expression like "+" as value but with working connection properties (which are checked in RelationalBaseSourceConnector#validate) the code assumes everything is fine to instantiate and validate the connection. But then, when instantiating an instance of the PostgresConnectorConfig the invalid regular expression gets compiled, leading to a PatternException.
This breaks the new PostgreSQL Connect REST Extension tests and it will also break Kafka Connect's validate connector-config endpoint (PUT /connector-plugins/($connector-plugin-name)/config/validate) which will also return the exception instead of the expected response with the config definition, errors, etc.