CYB-61: add Ruby auth client 

Any reason why this should not match this text from the Python README.md:

## Supported Actions

 - Fetch an access token from the authentication server with credentials supported by the active authentication mechanism;
 - Check if authentication is enabled in the gateway server; and
 - Invalidate any cached access tokens. 
 
 Current implementation supports three authentication mechanisms:
 - Basic Authentication
 - LDAP
 - JAASPI