Improve logging and error handling

[rustybee42]

Logging and error handling is currently in a not-so-ideal state as logs are not very detailed and sometimes the origin of an unexpected error is hard to find.

A couple of ideas to improve the situation:

• Use tracing crate instead of log - log doesn't keep track of async context, tracing does with its spans (increases compile time and binary size and adds more dependencies)
• Find a way to consistently log unexpected errors in detail so they can be easily tracked down to their origin
• Combine detailed logging with error handling or separate them where necessary
• Do not just return a complex log message to a gRPC requester - find a way to return user friendly text, but still log details on the server side, especially on unexpected errors
• ...

Specific improvements:

• Make quota logging less noisy and contain more info