I have successfully implemented the backend registration feature as per the requirements provided.
User Registration: Implemented the functionality to register new users.
User Update: Enabled users to update their information partially, including the ability to change email addresses.
User Deletion: Implemented user deletion functionality.
Error Handling: Added error handling for duplicate users.
Validation: Implemented validation checks for first name, last name, email, and password.
Email Address Uniqueness: Ensured that each user's email address is unique to prevent duplicate accounts during registration.
Email Address Update: Implemented functionality to allow users to update their email addresses. This includes validation to prevent conflicts with existing users' email addresses.
I have successfully implemented the backend registration feature as per the requirements provided.