Make audbcards independent from the used backend about audbcards

[hagenw]

To be able to still get information on author and date of publishing a database, I created audeering/audbackend#75 to support these for all backends.

/cc @Bahaabrougui

[hagenw]

Until audbackend is updated it might be that we have to skip Dataset.publication in the tests as it would make sense to use file-system based repository that is created on the fly in the tests.

[ChristianGeng]

I have used a dirty patch to circumvent the absence of publication here:

https://github.com/audeering/audbcards/pull/13/files#diff-9048213c5451377dd8ab1245088059131295d6a961d2f7bd2bb7017f2b572c7f:~:text=stat%20%3D%20path,return%20publication

So if this could be implemented, the ugliness of the above patch could also be remedied.

[hagenw]

In audbackend we have now added audbackend.Backend.owner() (== author) in audeering/audbackend#127 and are going to add audbackend.Backend.date() in audeering/audbackend#128, which means in the future those will be available independent of the backend. But as these are added to a version of audbackend that has breaking changes it might take some time until they will arrive in audb.

Until then it seems valid to me to add something like if self.repository.backend == 'file-system': to provide a workaround so we also have something there in the tests for the file-system backend.

[hagenw]

The same we could do for repository_link, e.g. just skip the link

if self.repository.backend == 'file-system':
    return self.repository}

[ChristianGeng]

So you say that for the time being, conditional execution depending on the backend type is ok, and the changes to audbackend are on their way, but patience is required, and no need to take initiative.

[hagenw]

Yes, exactly.