Let the Notify team invite people to an organisation

We want to start granting access to the org page. But it will be a bit
weird if the invites come from us personally, since the people we’re
inviting don’t know us.

It makes more sense, and sounds more official if the invites appear to
come from the ‘GOV.UK Notify team’ instead.

app/organisation/invite_rest.py

@@ -48,7 +48,11 @@ def invite_user_to_org(organisation_id):
         recipient=invited_org_user.email_address,
         service=template.service,
         personalisation={
-            'user_name': invited_org_user.invited_by.name,
+            'user_name': (
+                'The GOV.UK Notify team'
+                if invited_org_user.invited_by.platform_admin
+                else invited_org_user.invited_by.name
+            ),
             'organisation_name': invited_org_user.organisation.name,
             'url': invited_org_user_url(
                 invited_org_user.id,