♻️(backend) fallback to email identifier when no name (#1298)

In the UserlightSerializer, if the user has no short_name or full_name,
we have no info about the user. We decided to use the email identifier
and slugify it to have a little bit information.

src/backend/core/api/serializers.py

@@ -7,6 +7,7 @@ from base64 import b64decode
 from django.conf import settings
 from django.db.models import Q
 from django.utils.functional import lazy
+from django.utils.text import slugify
 from django.utils.translation import gettext_lazy as _
 
 import magic
@@ -32,11 +33,30 @@ class UserSerializer(serializers.ModelSerializer):
 class UserLightSerializer(UserSerializer):
     """Serialize users with limited fields."""
 
+    full_name = serializers.SerializerMethodField(read_only=True)
+    short_name = serializers.SerializerMethodField(read_only=True)
+
     class Meta:
         model = models.User
         fields = ["full_name", "short_name"]
         read_only_fields = ["full_name", "short_name"]
 
+    def get_full_name(self, instance):
+        """Return the full name of the user."""
+        if not instance.full_name:
+            email = instance.email.split("@")[0]
+            return slugify(email)
+
+        return instance.full_name
+
+    def get_short_name(self, instance):
+        """Return the short name of the user."""
+        if not instance.short_name:
+            email = instance.email.split("@")[0]
+            return slugify(email)
+
+        return instance.short_name
+
 
 class TemplateAccessSerializer(serializers.ModelSerializer):
     """Serialize template accesses."""