[BE] - "Update users" route should handle removing identity

[deepakvenkat]

As a logged in user, when I remove an identity from the front end, then data should be updated.

Bug :

1. Create a user with n identities ('Gay', 'Black', 'Male', 'Queer)
2. Using the PUT /users/:id route try to update the identities by removing one of them from the list. (i.e. send only 'Gay', 'Black', 'Male' in the identities_attributes)

Expected result

User should have only Gay, Black, Male in the identities list

Actual Result

User has : Gay, Black, Male, Queer, Gay, Black, Male in their identities list.

Notes

This is because the controller uses rails' relationship params to update identities which probably does not know how to deal with removing relationship data and just creates new relationship rows in the join table https://github.com/outintech/nbjc-app/blob/main/app/controllers/api/v1/users_controller.rb#L64