feat: Send welcome email from template

people/apps.py

@@ -1,5 +1,63 @@
+import logging
+
 from django.apps import AppConfig
+from django.conf import settings
+from django.core import serializers
+from django.db.models.signals import post_save
+
+logger = logging.getLogger(__name__)
+
+
+def load_welcome_template_fixture(fixture_path) -> bool:
+    """Load welcome email template from a JSON fixture."""
+    try:
+        with open(fixture_path) as f:
+            for deserialized in serializers.deserialize('json', f):
+                if deserialized.object.name == settings.TEMPLATE_WELCOME_EMAIL_NAME:
+                    deserialized.save()
+                    logger.warning('Welcome email template \'%s\' loaded', deserialized.object.name)
+                    return True
+
+            return False
+
+    except FileNotFoundError:
+        logger.warning('Email template fixture not found.')
+        return False
+
+
+def send_welcome_email(sender, instance, **kwargs):
+    from post_office import models
+
+    try:
+        instance.send_welcome_email()
+
+    except models.EmailTemplate.DoesNotExist:
+        logger.warning('Welcome email template \'%s\' not found - attempting to load from fixtures',
+                       settings.TEMPLATE_WELCOME_EMAIL_NAME)
+        
+        is_loaded = False
+        if settings.CUSTOMISATION_NAME:
+            # Customisation app present - try here first
+            is_loaded |= load_welcome_template_fixture(
+                settings.BASE_DIR.joinpath('custom', 'fixtures', 'email_templates.json')
+            )
+
+        # |= operator shortcuts - only try here if we don't already have it
+        is_loaded |= load_welcome_template_fixture(
+            settings.BASE_DIR.joinpath('people', 'fixtures', 'email_templates.json')
+        )
+
+        if is_loaded:
+            instance.send_welcome_email()
+
+        else:
+            logger.error('Welcome email template \'%s\' not found', settings.TEMPLATE_WELCOME_EMAIL_NAME)
 
 
 class PeopleConfig(AppConfig):
     name = 'people'
+    
+    def ready(self) -> None:
+        # Activate signal handlers
+        post_save.connect(send_welcome_email,
+                          sender='people.user')