✨(api) allow to list and create Mailboxes

Simply display all Mailboxes create for a MailDomain.
LDAP connection is not yet available, it will be implemented soon.
Read and create permissions will be refined soon too.

src/backend/mailbox_manager/api/serializers.py

@@ -0,0 +1,21 @@
+"""Client serializers for the People mailbox_manager app."""
+
+from rest_framework import serializers
+
+from mailbox_manager import models
+
+
+class MailboxSerializer(serializers.ModelSerializer):
+    """Serialize mailbox."""
+
+    class Meta:
+        model = models.Mailbox
+        fields = ["id", "local_part", "secondary_email"]
+
+
+class MailDomainSerializer(serializers.ModelSerializer):
+    """Serialize mail domain."""
+
+    class Meta:
+        model = models.MailDomain
+        fields = ["id", "name"]