Clean up MediaController and other media code

[ComputerGhost]

The MediaController endpoints are doing too much. Pull the logic into a service or something in the Business project.

And if we do this, is there any further need for the Media library? Consider it but of course don't move stuff out of there if it ends up not making sense to do so. ;)

[ComputerGhost]

Partially no longer existing after refactor. Reopen later if needed after they are readded.