enable the Croissant exporter by default (move code to main repo)

[pdurbin]

Overview of the Suggestion

Currently, the Croissant exporter is opt-in. You have to manually install it, as described at https://github.com/gdcc/exporter-croissant

What if new installations of Dataverse automatically got the Croissant exporter? We would keep the modularity. If they want to opt-out of Croissant, they would remove the Croissant jar file.

Alternatively, we could move the Croissant code from the external repo into the main Dataverse codebase. There would be no opt-out in the case, however.

What inspired this idea?

As of 6.5 we can query an API to see which exporters are enabled (#10739) and we've noticed that only 1 out of 13 has enabled it:

bonndata.uni-bonn.de             Datacite,dataversejson,dcterms,ddi,html,oaidatacite,oaidc,oaiddi,OAI_ORE,schema.org            6.5/1682-d9cc5eb         
darus.uni-stuttgart.de           Datacite,dataversejson,dcterms,ddi,html,oaidatacite,oaidc,oaiddi,OAI_ORE,schema.org            6.5/None         
data.tu-dortmund.de              Datacite,dataversejson,dcterms,ddi,html,oaidatacite,oaidc,oaiddi,OAI_ORE,schema.org            6.5/1682-d9cc5eb         
dataverse.dartmouth.edu          Datacite,dataversejson,dcterms,ddi,html,oaidatacite,oaidc,oaiddi,OAI_ORE,schema.org            6.5/1682-d9cc5eb         
dataverse.harvard.edu            croissant,Datacite,dataversejson,dcterms,ddi,html,oaidatacite,oaidc,oaiddi,OAI_ORE,schema.org  6.5/iqss-2         
dataverse.lib.unb.ca             Datacite,dataversejson,dcterms,ddi,html,oaidatacite,oaidc,oaiddi,OAI_ORE,schema.org            6.5/1682-d9cc5eb         
dataverse.orc.gmu.edu            Datacite,dataversejson,dcterms,ddi,html,oaidatacite,oaidc,oaiddi,OAI_ORE,schema.org            6.5/1682-d9cc5eb         
dataverse.theacss.org            Datacite,dataversejson,dcterms,ddi,html,oaidatacite,oaidc,oaiddi,OAI_ORE,schema.org            6.5/1682-d9cc5eb         
datosdeinvestigacion.udea.edu.co Datacite,dataversejson,dcterms,ddi,html,oaidatacite,oaidc,oaiddi,OAI_ORE,schema.org            6.5/1682-d9cc5eb         
edatos.consorciomadrono.es       Datacite,dataversejson,dcterms,ddi,html,oaidatacite,oaidc,oaiddi,OAI_ORE,schema.org            6.5/None         
edmond.mpdl.mpg.de               Datacite,dataversejson,dcterms,ddi,html,oaidatacite,oaidc,oaiddi,OAI_ORE,schema.org            6.5/mpdl-develop - 8eced947ba         
heidata.uni-heidelberg.de        Datacite,dataversejson,dcterms,ddi,html,oaidatacite,oaidc,oaiddi,OAI_ORE,schema.org            6.5/1682-d9cc5eb         
rdr.kuleuven.be                  Datacite,dataversejson,dcterms,ddi,html,oaidatacite,oaidc,oaiddi,OAIORE,rocratejson,schema.org 6.5/1682-d9cc5eb         

[pdurbin]

At tech hours yesterday we talked about the pros and cons of internal vs. external exporters.

This is what I wrote for our monthly meeting today:

• PD: I'm trying to get Trusted Data unblocked. In the backend PR I'll probably start limiting dataset types by collection and then move it to ready for review. Then, in a new PR, I'll copy the Croissant code into the main code base and work on implementing a short mode (more on this below) and move that to ready for review. Then, in a new PR, I'll work on upgrading to Croissant 1.1, including adding statistics. Then, in a new PR, I'll add inside-out Croissant for reviews, part of Trusted Data.
• PD: I'm evaluating Croissant 1.1. We might want to tell the spec leads that we're not ready to support statistics until we've come up with a way to offer a short version of Croissant without variables or perhaps even without files, as described above.

I think we should go ahead and move the Croissant code into the main code base.