fix(users.py): update error message to be more generic and not reveal specific reason for username unavailability

fix(AdminPage/index.tsx): fix nullish assertion for create_at and updated_at properties to avoid potential errors
fix(signUpPage/index.tsx): fix error handling to correctly display error message
fix(types/components/index.ts): make id, create_at, and updated_at properties optional in UserInputType

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

@@ -43,7 +43,7 @@ def add_user(
         db.refresh(new_user)
     except IntegrityError as e:
         db.rollback()
-        raise HTTPException(status_code=400, detail="This username is unavailable as it has already been claimed. Please choose a different username.") from e
+        raise HTTPException(status_code=400, detail="This username is unavailable.") from e
 
     return new_user