Small tweaks for adding a new application member:

- raise specific invitation type if invite not found in invitation domain classes
- more terse assignments of defaults in invitation service, smh
- terser margin expression for inline input fields
- sass formatting
- use translation for cancel link
- oxford comma for app team management permission explanation
- do not format environment roles with hyphens for role selection
- generalize some additional methods in the invitation domain base class
- use plain atst.models import path

translations.yaml

@@ -444,7 +444,7 @@ portfolios:
         manage_perms: 'Manage permissions for {application_name}'
         manage_envs: 'Allow member to <strong>add</strong> and <strong>rename environments</strong> within the application.'
         delete_envs: 'Allow member to <strong>delete environments</strong> within the application.'
-        manage_team: 'Allow member to <strong>add, update</strong> and <strong>remove members</strong> from the application team.'
+        manage_team: 'Allow member to <strong>add, update,</strong> and <strong>remove members</strong> from the application team.'
   index:
     empty:
       start_button: Start a new JEDI portfolio