`FetchLabelByReferenceUsecase` feels like a pure BIP329 usecase, better to have a getLabelById usecase now that we have id's. Or at least have both and if the callers that need this have the id it would be better if they fetch by id if possible.

[ethicnology]

[ethicnology]

I can add the id version, this has nothing to do with Bip329 but with the unique constraint in our database that guarantee us that a single label exists per reference