Feature/jyothiprakashpanaik/issue 43/feat editor table to store which user has access to edit which lists

[jyothiprakashpanaik]

Added Editor table:

User: Foreign Key
List: Foreign Key

• Owner of the list can add members/ other users to edit a list

Now added Users have the right to add problems to that list.

• Route : /lists​/userlist​/add bugfix: User is able to add problems to other user list. bugfix: User is able to add problems to other user list.  #36
  Users can view their own lists and shared lists.

• Route : /lists/user/:username feat: a route to get all lists of a user feat: a route to get all lists of a user #38

• test

[ShivamSinghal1]

"""
List Create -> Name - DP
Deafult - Private ( I can only access to that list )
I can change this list to Public
(Anyone with link can view that list )
Shared
(Any friend can share list)

    // Username
    // If Username == Authenticated User
    // I am seeing my own list 
    // Private List  Public List  Shared List ( My friend shared List )

    // If username != Authenticated User 
    // I am seeing other user list 
    // Other User Public List  // Other User Shared Public List  // Private List (NO)
    {
        'status': 'OK',
        'result': {
            'public': [

            ],
            'private': [

            ],
            'shared': [

            ]
        }
    }
    """