Allow to create an arbitrary length ASCII identifier

Summary:
Reference: https://neilmadden.blog/2018/08/30/moving-away-from-uuids/

Fixes T1609.

Test Plan: Unit tests added.

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1609

Differential Revision: https://devcentral.nasqueron.org/D2277