Allow commas (,) for `pulp_labels` values

[wcheang]

Is your feature request related to a problem? Please describe.
The new Konflux RPM signing workflow uses the pulp label signed_by to record signing keys used for signed RPMs. This label has to use an existing format that involves commas (e.g. release4,release2). However, commas are not currently supported by Pulp as label values.

Describe the solution you'd like
Please add support to use commas as pulp_labels values.

Describe alternatives you've considered
We could potentially use a format separate for the label values. However, since the values with commas are an existing convention that's used in the traditional pipelines, it'll be good for the values to stay consistent to ensure a smoother transition between the old and new RPM signing workflows.

Additional context
N/A

[dralley]

@wcheang Would it be possible / acceptable if you were able to escape the commas (e.g. \,) when setting pulp_labels? Or do you really need to use the strings release1,release2 verbatim. It would be a minor processing step though.

The core issue is that we use commas as the separator when setting pulp_labels, so we need to figure out how to force some alternative parsing mode that allows commas and presumably also allows setting multiple labels. Probably the most straightforwards thing is to just allow escaping the commas within values.

[wcheang]

I would like to be able to use the string verbatim as a user, but if the value is stored as the escaped version, that's fine. Essentially, it's okay if the actual label stored in the db is escaped (e.g. release1\,release2), as long as the pulp operations support the verbatim input release1,release2 (i.e. I can set the label with the input release1,release2, and I am able to search with the value release1,release2.

My concern here is that since the format release1,release2 is currently used in the traditional pipeline, when it's time to migrate workflow/content, it might cause confusion/errors if a different separator is used. Escaping the commas still require someone to be "in the know" about the escaping while interacting with Pulp, which makes it functionally no different than using a different symbol.

That being said, there aren't any transition plans yet. So if this change is too complicated or undesirable for Pulp to make, I'm okay with looking more into alternatives or at least taking more time to figure out what the actual impact would be.

[dralley]

I think the value could be stored as the release1,release2 form, it's just a matter of how the value gets provided to Pulp. So the opposite of that. The escaping is just needed to get the values through the Pulp API without mistaking them for different labels.

Anyway other solutions are maybe possible if that wouldn't work for you, it's just the most straightforwards option.

[dralley]

Actually I don't think setting it is an issue, the main issue is the query filters. The query filters permit multiple labels to be filtered on, separated by commas. So you would need to escape the commas in the query filters.

?pulp_label_select=signed_by=release1\,release2,somotherkey=foobar

Unless you don't plan to use those at all.