update user

### Feature: update User
>Create a new user in a database.
#### Pre-requisites:
- [ ] Complete create User feature
- [ ] user DAO( update user )
- [ ] user service ( update (User user) )
#### Validations:
- [ ] Form Validation
* update ( User user )
* user null
* name ( null, empty, pattern )
* email ( null, empty, pattern )
* password ( null, empty, pattern )
* phone number ( length, >= 600000001 && <= 9999999999 )
- [ ] Business Validation
* check the user Already exists
#### Messages:
* Invalid User object
* Invalid name input
* Invalid email input
* Invalid password input
* Invalid phone number input
* User not exists
#### Flow:
```mermaid
graph TD;

A[Value Passed to UserService - User Object] --> B[Form Validation & Business Validation]

B--> C{Validation Result}

C -- Valid --> D[Value Passed to UserDAO]

D --> E[update Value in Database]

C -- Invalid --> F[Validation Exception]
```

Start by reviewing the completed create User feature, then locate the user DAO and user service entry points described in the issue. Trace the validation flow for the User object and its fields before checking how database updates and existence errors are handled. Done means valid users update successfully, invalid inputs produce the listed messages, and nonexistent users are rejected.

Written by the indexing model from the issue text.