Which use case/requirement will be addressed by the proposed feature?

When using Oracle connector in RAC mode with the `rac.nodes` settings, it is always assumed the SID is identical to that of the main connection. The settings allows to override the port number for each node but not the SID.

Implementation ideas (optional)

Allow the `rac.nodes` to have a SID (dbname) by optionally specifying:
`rac.nodes=<ip>:<port>/<dbname>`
If /<service_name> is not present, will reuse the main SID. If <port> is not present, uses the main port (as it does today)