Last.fm Import does not work for large libraries

[davidsmind]

https://github.com/strawberrymusicplayer/strawberry/issues/1936

Cross posting the issue here in case someone else has found a userspace solution to this.

There is one shared api key for all strawberry users here, hardcoded in strawberry:
https://github.com/strawberrymusicplayer/strawberry/blob/afc3effc9d6bcfec83f60e9b90bd55dbac14c672/src/scrobbler/lastfmscrobbler.cpp#L69C13-L69C28

A possible solution would be to allow the user to specify last.fm api key, which they own, either manually (via an environment variable, config file or passed in argument) or via the ui.

Additionally, some more resilience (backoff llogic) would allow large libraries to eventually successfully be fetched even with the shared api key.