Don't allow the duplication of authorization numbers

[toraritte]

Authorization numbers are unique therefore they should be treated as such by the database as well but mostly because it is super error prone entering the same identifier by hand multiple times (as it is currently done).

Complicating factors:

1. Multiple service areas per authorization

   For example, AT, ILS, Braille, and O&M under one auth.

2. "TEMP" auths

   Sometimes auths are not received by us, but clients are supposed to start receiving services on a certain date. Also, the previous items applies here as well, that further complicates the situation, because there can be multiple TEMP auths, all of which could apply to multiple service areas.

[toraritte]

Composite key for authorization ID + service area? But what about TEMP authorizations?