REANA CAP Integration

[ParthS007]

We want to discuss how we can better integrate REANA with CAP ( mainly from a user authentication point of view).
Right now, we have global tokens ( by experiment or just a global one), so there can be many users associated with a token/experiment. It is not ideal to use a single token by any user of a single experiment (e.g more management from CAP side, no user quota respected, REANA side can't know who is using the resources, etc)
Moving ahead, we want to move the connection from an experiment to a single user so there is more control. Ideally, having a Connect with REANA would be great so that a user can connect the REANA account with CAP.
Proposals can be:

1. OAuth provider in REANA
2. Single REANA user token for use in CAP
3. Others

Let us know what do you think and we can move ahead with implementation.

@tiborsimko