Compensation action

* adds compensation action to compensation detail view
* adds adding/removing logic for compensation action
* adds bootstrap style to select fields in forms
* refactors UnitEnum into UnitChoices using models.TextChoices (Django 3.x)
* adds translations

compensation/urls.py

@@ -18,6 +18,7 @@ urlpatterns = [
     path('<id>/edit', edit_view, name='edit'),
     path('<id>/remove', remove_view, name='remove'),
     path('<id>/state/new', state_new_view, name='new-state'),
+    path('<id>/action/new', action_new_view, name='new-action'),
     path('<id>/deadline/new', deadline_new_view, name="new-deadline"),
 
     # Documents
@@ -41,4 +42,7 @@ urlpatterns = [
 
     # Generic state routes
     path('state/<id>/remove', state_remove_view, name='state-remove'),
+
+    # Generic action routes
+    path('action/<id>/remove', action_remove_view, name='action-remove'),
 ]