Simplify channel selection using radio buttons

This takes a similar approach as in the previous commit. Since the
"training channel" doesn't really exist, we need some extra code
to pre-select it if a service is already in training mode. As in
the previous commit, I've removed a few non-critical test cases
where we really don't need to test exhaustively.

Note that we also need some specific code to avoid pre-selecting an
option for non-broadcast services, which only used to work by fluke:
we would try to populate the field with (False, None, 'all'), which
isn't a valid combination, so nothing was selected.

app/main/forms.py

@@ -2392,14 +2392,14 @@ class ServiceBroadcastAccountTypeField(GovukRadiosField):
 
 
 class ServiceBroadcastChannelForm(StripWhitespaceForm):
-    channel = ServiceBroadcastAccountTypeField(
+    channel = GovukRadiosField(
         'Emergency alerts settings',
         thing='mode or channel',
         choices=[
-            ("training-test-all", "Training mode"),
-            ("live-test-all", "Test channel"),
-            ("live-severe-all", "Live channel"),
-            ("live-government-all", "Government channel"),
+            ("training", "Training mode"),
+            ("test", "Test channel"),
+            ("severe", "Live channel"),
+            ("government", "Government channel"),
         ],
     )
 

app/main/views/service_settings.py

@@ -321,25 +321,27 @@ def service_set_permission(service_id, permission):
 @main.route("/services/<uuid:service_id>/service-settings/broadcasts", methods=["GET", "POST"])
 @user_is_platform_admin
 def service_set_broadcast_channel(service_id):
-    form = ServiceBroadcastChannelForm(
-        channel=(
-            current_service.live,
-            current_service.broadcast_channel,
-            'all',
-        )
-    )
+    if current_service.has_permission('broadcast'):
+        if current_service.live:
+            channel = current_service.broadcast_channel
+        else:
+            channel = 'training'
+    else:
+        channel = None
+
+    form = ServiceBroadcastChannelForm(channel=channel)
 
     if form.validate_on_submit():
-        if form.channel.service_mode == 'training':
+        if form.channel.data == 'training':
             return redirect(url_for(
                 '.service_confirm_broadcast_account_type',
                 service_id=current_service.id,
-                account_type=form.channel.data,
+                account_type='training-test-all'
             ))
         return redirect(url_for(
             '.service_set_broadcast_network',
             service_id=current_service.id,
-            broadcast_channel=form.channel.broadcast_channel,
+            broadcast_channel=form.channel.data,
         ))
 
     return render_template(

tests/app/main/views/test_service_settings.py

@@ -5537,28 +5537,14 @@ def test_service_set_broadcast_channel_has_no_radio_selected_for_non_broadcast_s
             "test",
             "all",
             "Training mode",
-            "training-test-all",
-        ),
-        (
-            "live",
-            "test",
-            "vodafone",
-            "Test channel",
-            "live-test-all",
-        ),
-        (
-            "live",
-            "severe",
-            "all",
-            "Live channel",
-            "live-severe-all",
+            "training",
         ),
         (
             "live",
             "government",
             "all",
             "Government channel",
-            "live-government-all",
+            "government",
         ),
     ]
 )
@@ -5598,25 +5584,25 @@ def test_service_set_broadcast_channel_has_radio_selected_for_broadcast_service(
 
 
 @pytest.mark.parametrize(
-    'account_type,expected_redirect_endpoint,extra_args',
+    'channel,expected_redirect_endpoint,extra_args',
     [
         (
-            'training-test-all',
+            'training',
             '.service_confirm_broadcast_account_type',
             {'account_type': 'training-test-all'},
         ),
         (
-            'live-test-all',
+            'test',
             '.service_set_broadcast_network',
             {'broadcast_channel': 'test'},
         ),
         (
-            'live-severe-all',
+            'severe',
             '.service_set_broadcast_network',
             {'broadcast_channel': 'severe'},
         ),
         (
-            'live-government-all',
+            'government',
             '.service_set_broadcast_network',
             {'broadcast_channel': 'government'},
         ),
@@ -5626,7 +5612,7 @@ def test_service_set_broadcast_channel_redirects(
     client_request,
     platform_admin_user,
     mocker,
-    account_type,
+    channel,
     expected_redirect_endpoint,
     extra_args,
 ):
@@ -5635,7 +5621,7 @@ def test_service_set_broadcast_channel_redirects(
         'main.service_set_broadcast_channel',
         service_id=SERVICE_ONE_ID,
         _data={
-            'channel': account_type,
+            'channel': channel,
         },
         _expected_redirect=url_for(
             expected_redirect_endpoint,