chore(): small infrastructure refactoring, improves and fixes

src/backend/api/v1/users/schemas.py

@@ -33,7 +33,6 @@ class UserCreateIn(ModelSchema):
 
 
 class UserUpdateIn(ModelSchema):
-    username: str | None = None
     email: str | None = None
     first_name: str | None = None
     last_name: str | None = None
@@ -41,7 +40,6 @@ class UserUpdateIn(ModelSchema):
     class Meta:
         model = User
         fields: ClassVar[tuple[str, ...]] = (
-            User.username.field.name,
             User.email.field.name,
             User.first_name.field.name,
             User.last_name.field.name,