display when a custom domain is created and number of aliases

app/dashboard/templates/dashboard/custom_domain.html

@@ -21,6 +21,10 @@
                 <i class="fe fe-check" style="color: green"></i>
               {% endif %}
             </h5>
+            <h6 class="card-subtitle mb-2 text-muted">
+              Created {{ custom_domain.created_at | dt }} <br>
+              <span class="font-weight-bold">{{ custom_domain.nb_alias() }}</span> aliases.
+            </h6>
 
             {% if not custom_domain.verified %}
               <hr>

app/models.py

@@ -631,3 +631,6 @@ class CustomDomain(db.Model, ModelMixin):
     domain = db.Column(db.String(128), unique=True, nullable=False)
 
     verified = db.Column(db.Boolean, nullable=False, default=False)
+
+    def nb_alias(self):
+        return GenEmail.filter_by(custom_domain_id=self.id).count()