feat: set arbitrary service hostname via annotation

[pl4nty]

Fixes #14

Tested with ghcr.io/pl4nty/external-mdns

[iamasmith]

It strikes me that if this were multi-value with an annotation like /hostnames, possibly comma separated, then this would also offer a workaround for #21 as well.
I'll pull your branch, rework and test and offer it back to you to consider as an update to this PR if that sounds reasonable?
Actually, I just took a quick look, this is a bigger change than I first thought and won't really leave anything of your original code.
I'll raise a separate PR but ack you on it.

[iamasmith]

Alt PR here allowing multiple hostnames and the ability to selectively turn on the more global without-default option for a specific service #22

[blake]

Hi @pl4nty, thanks for the contribution. I think this is a great addition.

@iamasmith's recent PR includes your work as well as some additional enhancements. Would you be opposed to me closing this PR in favor of #22?

[pl4nty]

Sounds good, I'm happy to build/test the replacement PR too