Improve registrar area linked user switch

- Introduce profile
- Move linked users to profile
- Use PUT

#599

app/presenters/user_presenter.rb

@@ -0,0 +1,19 @@
+class UserPresenter
+  def initialize(user:, view:)
+    @user = user
+    @view = view
+  end
+
+  def login_with_role
+    "#{user.login} (#{role_name}) - #{user.registrar_name}"
+  end
+
+  private
+
+  def role_name
+    user.roles.first
+  end
+
+  attr_reader :user
+  attr_reader :view
+end