Currently, the code for e.g. `/service` endpoint handling does it in a very rudimentary way . With the improvements of the error handling introduced in  it is now possible to replace all the block like  with a call to `util.exit_by_code`. The only thing that is needed is a way to handle custom error messages - making error pages accept the reason for the error as a parameter.
Acceptance criteria: All AR code uses `util.exit_by_code` call for emitting errors to the user.