OAuth Apps: delete duplicates and add a unique index on :client_name
Received a report from sun@spw that they have some errors in their logs with hundreds of apps with the same name (PleromaFE_timestamp) in their table. Not sure how so many were created with the same timestamp but we can just fix it with a unique index and drop the duplicates.
This will delete some oauth tokens as a side effect but it's possible they're not ones being used for users to login with.