This relationship is via the `Organisation` now; we don’t use this
column to fudge a relationship based on the user’s email address and the
matching something in these columns.
The admin app still needs to use the name column.
Add the text field to the post data schemas.
If the text is not in the post data, then populate it with the data in the name field.
This should make the migration to text easier, and will work until we are able to update the admin app.
notable things that have been kept until migration is complete:
* passing in `organisation` to update_service will update email branding
* both `/email-branding` and `/organisation` hit the same code
* service endpoints still return organisation as well as email branding
