Add UID for Account

[MV-GH]

Currently we use the id of of the user as unique account identifier. Here in lays the problem, this account id is not unique across instances. Meaning it is possible that user A from instance IA has the same ID as user B from IB.

Thus instead we should add a UID (incremental) as primary and drop the unique constraint for id.

Suggestions for naming of this column? iid, uid, sid..

[dessalines]

Any of those work for me. We'll probably have to copy and rebuild the table in a migration.

[MV-GH]

Yeah I'll pick this up once I do some changes to the db schema