Script to migrate user roles

[sumitd94]

This PR contains the migration script, which will be running only once which will remove the isMember field, and add a new field roles which will be an object something like this

{
 roles: { member: true }
}

All those users who have isMember set to true, will have member: true in the roles objects, and for the rest of all users, member: false

endpoint - https://api.realdevsquad.com/members/member-to-role-migration

[ankurnarkhede]

@sumitd94 , executing this will solve the failing tests in #296, right?
Also, is there any other way to execute this query or adding the route is the only way?

[ankurnarkhede]

LGTM ✅