Only show relevant user permissions for broadcast services

For services with the broadcast permission this hides:
- the ‘View dashboard’ permission (and defaults it to _checked_) because
  all users of broadcast services will need to see the dashboard
- the ‘Manage API keys’ permission (and defaults it to _not checked_)
  because we don’t offer an API integration for broadcast services yet
  – if we do we won’t want existing users to automatically get the
  permission

It relabels:
- the ‘Send’ permission to ‘Prepare and approve’ to match the current,
  slightly clunky language on the templates page
- the ‘Manage settings’ label to not refer to ‘usage’ because broadcast
  services won’t incur cost

app/main/views/manage_users.py

@@ -18,6 +18,8 @@ from app.event_handlers import (
 )
 from app.main import main
 from app.main.forms import (
+    BroadcastInviteUserForm,
+    BroadcastPermissionsForm,
     ChangeEmailForm,
     ChangeMobileNumberForm,
     ChangeNonGovEmailForm,
@@ -47,7 +49,12 @@ def manage_users(service_id):
 @user_has_permissions('manage_service')
 def invite_user(service_id):
 
-    form = InviteUserForm(
+    if current_service.has_permission('broadcast'):
+        form_class = BroadcastInviteUserForm
+    else:
+        form_class = InviteUserForm
+
+    form = form_class(
         invalid_email_address=current_user.email_address,
         all_template_folders=current_service.all_template_folders,
         folder_permissions=[f['id'] for f in current_service.all_template_folders]
@@ -89,7 +96,12 @@ def edit_user_permissions(service_id, user_id):
     if user.mobile_number:
         mobile_number = redact_mobile_number(user.mobile_number, " ")
 
-    form = PermissionsForm.from_user(
+    if current_service.has_permission('broadcast'):
+        form_class = BroadcastPermissionsForm
+    else:
+        form_class = PermissionsForm
+
+    form = form_class.from_user(
         user,
         service_id,
         folder_permissions=None if user.platform_admin else [