[New API Needed] About user backend

[jyeok]

I think we need some modification / additional api:

1. I think our servcies doesn't have to need user's age, phone_number, gender. It is good for remain optional fields. I think we can let user select they can submit addtional (not-essential) information on signing-up or edit it on their my page.

2. We need the api which returns user's id when the user's username (not nickname) is given. (-1 when not found). We have to develop duplicated ID check feature.

[ByungHeeCha]

Should I make branch from dev or master?

[jyeok]

I think we need to modify the signup POST method to return the dictionary of newly created user information with given ID. Using that we can implement uploading of profile picture.

[jaehonam]

I have changed codes @jyeok mentioned.

1. signup post method returns id
2. signup post method and user put method don't requires age, phone_number, gender.
3. new signup_dupcheck post method added.
   url : /api/signup_dupcheck/
   requires : content-type = application/json, {'username': string}
   returns : json type {'id': some pos integer if username exist, -1 o.w.}