[Story] Pluggable Discovery Database

[andrewazores]

Parent: https://github.com/cryostatio/cryostat/issues/936

To serve the needs of parent 3, we should add some form of database container to the Cryostat deployment. This needs to be able to hold information about target applications as well as their parent nodes in the deployment graph - so in OpenShift, from the Namespace, to Deployment(Config), to Pod, to Replica, to Endpoint, or some similar variations.

Once we determine what type of database this will be (ex SQL vs NoSQL) we should solidify on a design that allows Cryostat to be configured to point to and connect to that database, including with optional credentials and authentication. The database container should be able to be one supplied in advance by the end user, or one set up by the Operator if the user does not provide their own.

• [x] https://github.com/cryostatio/cryostat/issues/941
• [ ] https://github.com/cryostatio/cryostat/issues/942
• [ ] https://github.com/cryostatio/cryostat/issues/943