replace ID with UID

[Allan Bowe]

In addressing #359 it was discovered that the sequencing utility was broken in COSMODB (set every id to 1)

In general, sequencing (surrogate key) isn't a great approach as it provides a bottleneck in generating the latest id (and avoiding RACE conditions)

For scalability, and to simplify the process, we should switch away from IDs and use UUIDs in the following schemas:

• Users
• Groups
• Permissions