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': [ ] } } """