Users who work in local government can’t have GOV.UK branding on their
emails. And only those working for Companies House (for example) can
request the Companies House branding.
This commit adds:
- new choices of email branding, which offer the name of the branding,
rather than the style
- logic to filter this list to only the applicable options, based on
what we know about the user, service and organisation
This is a change from the previous approach which put the onus on users
to figure out the style of branding they wanted, when we might already
know that a lot of the options weren’t available to them, or would be
inconsistent with the branding of other services in their organisation.