send email upon extension + nit

backend/clubs/models.py

@@ -1603,6 +1603,25 @@ class ApplicationExtension(models.Model):
     )
     end_time = models.DateTimeField()
 
+    def send_extension_mail(self):
+        context = {
+            "name": self.user.first_name,
+            "application_name": self.application.name,
+            "end_time": self.end_time,
+            "club": self.application.club.name,
+            "url": (
+                f"https://pennclubs.com/club/{self.application.club.code}"
+                f"/application/{self.application.pk}/"
+            ),
+        }
+
+        send_mail_helper(
+            name="application_extension",
+            subject=f"Application Extension for {self.application.name}",
+            emails=[self.user.email],
+            context=context,
+        )
+
     class Meta:
         unique_together = (("user", "application"),)
 

backend/clubs/serializers.py

@@ -2476,15 +2476,14 @@ def validate(self, data):
         if not application:
             raise serializers.ValidationError("Invalid application id!")
 
-        if (
-            (
-                not self.instance
-                or (username and self.instance.user.username != username)
-            )
-            and ApplicationExtension.objects.filter(
-                user=user, application=application
-            ).exists()
-        ):
+        application_exists = ApplicationExtension.objects.filter(
+            user=user, application=application
+        ).exists()
+        modify_username = not self.instance or (
+            username and self.instance.user.username != username
+        )
+
+        if modify_username and application_exists:
             raise serializers.ValidationError(
                 "An extension for this user and application already exists!"
             )
@@ -2500,6 +2499,11 @@ def validate(self, data):
 
         return data
 
+    def save(self):
+        extension_obj = super().save()
+        extension_obj.send_extension_mail()
+        return extension_obj
+
 
 class ApplicationSubmissionSerializer(serializers.ModelSerializer):
     committee = ApplicationCommitteeSerializer(required=False, read_only=True)

backend/templates/emails/application_extension.html

@@ -0,0 +1,22 @@
+<!-- TYPES:
+name:
+    type: string
+club:
+    type: string
+application_name:
+    type: string
+end_time:
+    type: string
+url:
+    type: string
+-->
+{% extends 'emails/base.html' %}
+
+{% block content %}
+    <h2>Application Extension for {{ application_name }}</h2>
+    <p style="font-size: 1.2em;">Hello {{ name }},</p>
+    <p style="font-size: 1.2em;">You have been granted an extension for {{ application_name }} by the officers of {{ club }} on Penn Clubs:</p>
+    <p style="font-size: 1.2em;">The updated deadline to submit your application is {{ end_time }}. You can apply using the button below.</p>
+    <a style="text-decoration: none; padding: 5px 20px; font-size: 1.5em; margin-top: 25px; color: white; background-color: green; border-radius: 3px; font-weight: bold"
+        href="{{ url }}">Apply</a>
+{% endblock %}