Change `role` to Credit

[Jomula]

Right now, the role field in contacts refers to our internal role taxonomy. We should change it to an array and insert the CRediT PIDs, e.g. 0c8ca7d4-06ad-4527-9cea-a8801fcb8746 for Supervision (or even the whole URI).

[theodore-s-beers]

I've mostly taken care of this in #375. role became roles. It's now an array, each of whose values must belong to a defined set of strings, representing the CRediT roles. (This uses the enum type in Zod; we do the same thing to validate keywords.)

What used to be our role 0 became supervision. The old role 1 became investigation. I don't know whether this was ideal in every case, but I didn't see better options for blanket changes. NB: 0 and 1 were the only roles in the previous system that we were actually using. @XeniaMonika, we now have a lot more options in this part of the schema. There are fourteen roles to choose from, and a given contact can be assigned more than one of them. It's something to think about in terms of maintaining/updating existing entries in our database, as well as adding new projects.

The schema version has been bumped from 0.2.0 to 0.2.1. @XeniaMonika, this will require another brief entry in the schema changelog.

@Jomula, I haven't added the role PIDs yet. How should that work? Should each role be an object with name and id fields?

[Jomula]

I think object with name and id would be perfect, this would make it possible to refer to the PID, but also provides a way to simply read the name of the role in the data.

[theodore-s-beers]

I've done a bit more on this in #388.

@Jomula, as you can see, for the time being I've gone with (name, id) tuples instead of objects. It's just a more compact type. Let me know if this seems problematic.

So far the role IDs have been added only in the schema. i.e., in a roles array in a project JSON file, it will still just be a list of role names. I can change that once I know that people are ok with using tuples. (You can imagine that, if multiple roles were listed for a given contact, an array of tuples would look less messy than an array of objects.)

[Jomula]

I'm fine with tuple arrays, as long as it's properly documented!