Content support: Generate error messages for manage.get.gov

[abroddrick]

Issue description

We did an audit of error logs for the domain request form a while ago (#1247) and now that org model is nearing MVP completion we should update our documented error messages so they can be audited.

Acceptance criteria

• as a dev, go through the code and update the error messages document with new or changed errors, be sure to indicate when this error can occur
  • some errors are extremely unlikely, be sure to convey that in the document if it is an error that no user in non-test envs should see

Additional context

No response

Links to other issues

• relates to Content review support: Generate error messages for manage.get.gov #1247

[abroddrick]

@Katherine-Osos we originally talked about just scoping this to org model member management, but if we are looking at errors anyway it seems like we should just update the documentation for all errors. Would that be too much for design to review at once? If so, happy to reduce the scope of this.

[abroddrick]

This was brought up in org model again, and the thumbs up was given to update documentation for all errors