This PR is handles the changes required to support envelopes. The new
envelope editor/signing page will be hidden during release.
The core changes here is to migrate the documents and templates model to
a centralized envelopes model.
Even though Documents and Templates are removed, from the user
perspective they will still exist as we remap envelopes to documents and
templates.
## Changes Made
- Refactor/optimise tests
- Reduce flakiness
- Add parallel tests (if there's enough CPU capacity)
- Removed explicit worker count when running parallel tests. Defaults to
50% of CPU capacity.
Might want to consider sharding the test across runners in the future as
our tests grows.
