routes.rb

namespace :api, defaults: { format: :json } do
    namespace :v1 do
      mount_devise_token_auth_for 'User', at: 'auth', skip: [:omniauth_callbacks] # add this and overide the omniauth callbacks
      post 'social_auth/callback', to: 'social_auth_controller#authenticate_social_auth_user' # this is the line where we add our routes
    end
  end