Use kratos api for looking up user by email address

backend/helpers/kratos_user.py

@@ -150,23 +150,12 @@ class KratosUser():
 
         kratos_id = None
 
-        # Get out user ID by iterating over all available IDs
-        page = 0
-        while page >= 0:
-            if page == 0:
-                data = api.list_identities(per_page=1000)
-            else:
-                data = api.list_identities(per_page=1000, page=page)
-            for kratos_obj in data:
-                # Unique identifier we use
-                if kratos_obj.traits['email'] == email:
-                    kratos_id = str(kratos_obj.id)
-                    return KratosUser(api, kratos_id)
-            if len(data) == 0:
-                page = -1
-            else:
-                page = page + 1
-
+        data = api.list_identities(credentials_identifier=email)
+        for kratos_obj in data:
+            if kratos_obj.traits['email'].lower() == email.lower():
+                kratos_id = str(kratos_obj.id)
+                return KratosUser(api, kratos_id)
+        # No user found with matching email address.
         return None
 
     @staticmethod