Move roles to models file

Any time we can keep code out of the view files is good. This user stuff
seems like a sensible place to put it, since we’re going to use it
there.

app/main/views/manage_users.py

@@ -20,17 +20,10 @@ from app.main.forms import (
     PermissionsForm
 )
 from app import (user_api_client, current_service, service_api_client, invite_api_client)
+from app.notify_client.models import roles
 from app.utils import user_has_permissions
 
 
-roles = {
-    'send_messages': ['send_texts', 'send_emails', 'send_letters'],
-    'manage_templates': ['manage_templates'],
-    'manage_service': ['manage_users', 'manage_settings'],
-    'manage_api_keys': ['manage_api_keys']
-}
-
-
 @main.route("/services/<service_id>/users")
 @login_required
 @user_has_permissions('view_activity', admin_override=True)