Agency Update - Enable view and edit of docs in migration release

Updates from last week:

✅

Fix PUT for draft documents (and enable PUT for documents in a release!)

Thanks to the method we identified in order to create a new version of a previously unpublished draft document in the Migration Release, we now have a uniform way of updating documents via the Migration API:
- if a version of the document already exists in the Migration Release, it's updated in migration release
- if a version of the document exists as a draft or published version elsewhere, a new version is created in the migration release

As an extra bonus from this change, it is now also possible to update a document that is in a normal release. Doing so will result in a new version of that document being created in a migration release.

✅

Release M2M token fix for Migration API and Asset API (with security fix for Auth)

The permanent token (M2M token) for authentication is back in production after we fixed a security issue that was uncovered a few weeks back. We are monitoring closely today and will announce this to customers who have reported issues with auth tomorrow.

Goals for the next week:

Start work to enable documents in migration release to be viewed and edited

One major complaint about migration releases is that documents cannot be viewed and, if necessary, edited, before bulk publishing. Therefore, we want to enable this and make it even more beneficial to use migration releases. We expect to have this work ready for review and testing by the end of the week.