Allow terms metadata to be changed with Native API

[jggautier]

Some users want to be able to change Terms of Use metadata for multiple datasets in bulk (without need to open and edit each dataset's metadata). Users can use the Native API to add or edit metadata in the metadata fields that are in Dataverse's metadata blocks, but as of 4.19 the Native API doesn't let users do the same for Terms of Use and Terms of Access fields (in the Terms tab). In fact, if you use the "Update Metadata" endpoint to create or edit a dataset draft, which will overwrite any existing dataset metadata, all values in the Terms of Use and Terms of Access fields are also removed.

It would also be helpful to document in some brief way which fields can and can't be edited using the Native API.

(This is following discussion from the related issue at #2585)

[djbrooke]

• We want the granular option to edit terms, specifically the values of metadata fields in the "Terms of Use" and "Restricted Files + Terms of Access" panels (see screenshot)
• Add docs for what works and what does not work
• We'd want the workflow to be the same as what's in the UI, in that the option to provide terms is only available to those users deselecting CC0 and creating a new dataset version
• Do we want to just accept terms JSON that people send and automatically waive CC0 (do we do it silently or do we provide info)? - we want to provide info per @djbrooke

[pdurbin]

Yesterday at standup I said I'd push what I have (which isn't much) to a branch so here it is: pdurbin@60ff805

One thing I re-discovered along that way is that we already have an API to enable or disable the "Request Access" button: http://guides.dataverse.org/en/4.19/api/dataaccess.html#allow-access-requests

Here's a dump of the doc I stubbed out, which gives an idea of where my head's at:

Changing Terms and Licenses
~~~~~~~~~~~~~~~~~~~~~~~~~~~

curl -X GET /terms

curl -X POST /terms

{
  "specialPermissions": "so special",
  "depositorRequirements": "dance",
  "requestAccess": true,
  "license": "CC-BY"
}

(This would be an error since CC-BY is not supported.)

curl -X DELETE /terms/disclaimer

[jggautier]

Interesting!

(This would be an error since CC-BY is not supported.)

Just posting for consideration that the SWORD API guide describes similar logic, in the section with the crosswalk, where if the given xml file has dcterms:license set to "CC0," the CC0 waiver is retained. Otherwise, "enter “NONE” and fill in the dcterms:rights field".

Could this functionality borrow that logic? E.g. users who don't want to use CC0 for license should enter NONE, and for termsOfUse enter CC-BY (and even better, include the URL https://creativecommons.org/licenses/by/2.0)?