Adding robot SciToken support

I will now be working on adding support for robot SciTokens within GraceDB. My understanding of how to do this is to modify the update_user_accounts_from_ligo_ldap.py management tool to scan the ldap for new robot scitoken accounts, create/modify accounts as needed, and then apply the per-pipeline permissions to those accounts as needed.

@satyanarayan.raypitambarmohapatra, @warren-anderson, what is the status of robot accounts within the ldap? Its been a while since I've looked at them, but my understanding is that they each have an eppn that will link a robot scitoken to an ldap account?

Including @duncanmmacleod in this issue.