Use class constants instead of strings for 'generic' and 'genericmessage'

[1int]

Summary

This is a trivial change so I decided not to make an issue for it.

This PR replaces occurrences of 'generic' and 'genericmessage' with class constants to improve code clarity and prevent typos. Having class constants with proper comments also helps understand the expected behaviour.

[noplanman]

Thanks, hadn't thought of that!

I do think however, that it makes more sense to use GENERIC_COMMAND instead of FALLBACK_COMMAND, because fallback could mean anything.

Also, please add a short entry in the changelog in the Unreleased - Added section, thanks.

[1int]

Yeah I was doubting between GENERIC_COMMAND and FALLBACK_COMMAND myself :)
I chose FALLBACK_COMMAND because I think it reflects the point of that command better — if nothing else suits, fall back to this.

Ok, I'll make these changes today. Cheers!

[1int]

Updated

[noplanman]

Perfect, thanks!

[1int]

@noplanman hey, I also thought that now that there're constants it would possibly be good to rename 'genericmessage' to 'genericMessage' camel-case? Then you could have more consistent naming with GenericMessageCommand instead of GenericmessageCommand.

I can make another PR if you think it makes sense.

[noplanman]

The whole command system is quite complex and needs a rewrite in general, so I think it makes sense to leave it as is for the moment, but thanks so much for the suggestion!