Please provide your original free response answer and explanation to this prompt, thank you.

Imagine a situation in which you are storing information about a web-based application's users, in which each user has a username consisting of a string of uppercase letters, lowercase letters, and digits. It is not important what the application is, but imagine its most common operations are to add new users to the application and to check if user with a username already exists.

You decide that a hash table is how you would solve this problem, because you understand that a well-chosen hash function can be done akin to (1) lookups and amortized (1) insertions. Suppose that you have chosen a hash function that sums the character codes associated with the characters in the username.

Is the chosen hash function a good hash function? If so, provide a short explanation as to why it's sufficient; if not, briefly explain what's wrong with it. You do not need to propose a new hash function.