The goal of pluggable authentication is to enable the use of external systems as sources of data for authenticating users connecting to RSCDS.
An other secondary goal would be to support having the external source also provide the relationship information used by RSCDS to control permissions between users.
Implement a hook in the login process.
At this point the planned system will not meet the secondary goal. To meet the secondary goal would require some recoding of those functions which calculate permissions to use library functions, which would also need to be written.