Message service backend setup: switch config form per-service in the UI

See #281, which this commit prepares for

alerts/forms.py

@@ -3,7 +3,7 @@ from django.forms import ModelForm
 from .models import MessagingServiceConfig
 
 
-class MessagingServiceConfigForm(ModelForm):
+class MessagingServiceConfigNewForm(ModelForm):
 
     def __init__(self, project, *args, **kwargs):
         super().__init__(*args, **kwargs)
@@ -19,3 +19,13 @@ class MessagingServiceConfigForm(ModelForm):
         if commit:
             instance.save()
         return instance
+
+
+class MessagingServiceConfigEditForm(ModelForm):
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+
+    class Meta:
+        model = MessagingServiceConfig
+        fields = ["display_name"]

alerts/migrations/0004_alter_messagingserviceconfig_kind.py

@@ -14,7 +14,7 @@ class Migration(migrations.Migration):
             model_name="messagingserviceconfig",
             name="kind",
             field=models.CharField(
-                choices=alerts.models.kind_choices, default="slack", max_length=20
+                choices=alerts.models.get_alert_service_kind_choices, default="slack", max_length=20
             ),
         ),
     ]

alerts/models.py

@@ -6,7 +6,7 @@ from .service_backends.mattermost import MattermostBackend
 from .service_backends.discord import DiscordBackend
 
 
-def kind_choices():
+def get_alert_service_kind_choices():
     # As a callable to avoid non-DB-affecting migrations for adding new kinds.
     # Messaging backends don't need translations since they are brand names.
     return [
@@ -16,12 +16,22 @@ def kind_choices():
     ]
 
 
+def get_alert_service_backend_class(kind):
+    if kind == "discord":
+        return DiscordBackend
+    if kind == "mattermost":
+        return MattermostBackend
+    if kind == "slack":
+        return SlackBackend
+    raise ValueError(f"Unknown backend kind: {kind}")
+
+
 class MessagingServiceConfig(models.Model):
     project = models.ForeignKey(Project, on_delete=models.DO_NOTHING, related_name="service_configs")
     display_name = models.CharField(max_length=100, blank=False,
                                     help_text='For display in the UI, e.g. "#general on company Slack"')
 
-    kind = models.CharField(choices=kind_choices, max_length=20, default="slack")
+    kind = models.CharField(choices=get_alert_service_kind_choices, max_length=20, default="slack")
 
     config = models.TextField(blank=False)
 
@@ -40,13 +50,7 @@ class MessagingServiceConfig(models.Model):
                                                   help_text="Error message from the exception")
 
     def get_backend(self):
-        if self.kind == "discord":
-            return DiscordBackend(self)
-        if self.kind == "mattermost":
-            return MattermostBackend(self)
-        if self.kind == "slack":
-            return SlackBackend(self)
-        raise ValueError(f"Unknown backend kind: {self.kind}")
+        return get_alert_service_backend_class(self.kind)(self)
 
     def clear_failure_status(self):
         """Clear all failure tracking fields on successful operation"""

alerts/service_backends/discord.py

@@ -203,7 +203,8 @@ class DiscordBackend:
     def __init__(self, service_config):
         self.service_config = service_config
 
-    def get_form_class(self):
+    @classmethod
+    def get_form_class(cls):
         return DiscordConfigForm
 
     def send_test_message(self):

alerts/service_backends/mattermost.py

@@ -185,7 +185,8 @@ class MattermostBackend:
     def __init__(self, service_config):
         self.service_config = service_config
 
-    def get_form_class(self):
+    @classmethod
+    def get_form_class(cls):
         return MattermostConfigForm
 
     def send_test_message(self):

alerts/service_backends/slack.py

@@ -222,7 +222,8 @@ class SlackBackend:
     def __init__(self, service_config):
         self.service_config = service_config
 
-    def get_form_class(self):
+    @classmethod
+    def get_form_class(cls):
         return SlackConfigForm
 
     def send_test_message(self):