Implement impersonating users & roles in App & API

Summary Admin users will be able to send the headers x-impersonate-user and x-impersonate-role. The API would then treat the user to have the given role / user id for all intents and purposes (permissions, presets etc). There will also be a selector in the App for configuring if those headers are sent to the API. This selector should be easy to reach & refresh all data when changed Basic Example _No response_ Motivation When developing a backend with multiple roles and role-specific presets mistakes can be easily overlooked, especially if users also have their own presets. I'm often confronted with problems that users have which are either role- or user specific. Having a way to impersonate users during QA and when responding to support tickets would make life a lot easier. The current solution of either creating dummy users, or temporarily resetting user's passwords (making them reset it again after) is not good enough. The extended idea of being able …