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.
Allow organisations to manage an SSO OIDC compliant portal. This method
is intended to streamline the onboarding process and paves the way to
allow organisations to manage their members in a more strict way.
