Add/clarify OAI-PMH documentation

[kspurgin]

Purpose / why

Reading the OAI-PMH documentation page yesterday did not answer a couple of questions I had. I asked those questions in Slack. After seeing the answers in Slack, I realized part of the answers were implicit in the existing documentation page, but not really clear if you are coming to this fresh.

What changes were made?

• Adds two new sections to the OAI-PMH doc page: OAI-DC Metadata Format/Metadata Mappings and Creating additional metadata formats
• Reorganizes some of the existing documentation content into these two sections, and adds some additional information to them
• Clarifies that the "OAI Dublin Core (RDF Mapping)" you see in the OAI config is not a separate RDF mapping
• Adds link to example metadata format plugin

Verification??

These edits are based on responses from @seth-shaw-unlv and @jordandukart in Slack (here and here(thread)

They may wish to verify I have not misrepresented their responses in working them into the documentation page.

Interested Parties

@Islandora/documentation

Checklist

Pull-request reviewer should ensure the following

• Does this PR link to related issues?
• Does the proposed documentation align with the Islandora Documentation Style Guide?
• Are the changes accurate, useful, free of typos, etc?

Person merging should ensure the following

• Does mkdocs still build successfully? (This is indicated by TravisCI passing. To test locally, and see warnings, see How To Build Documentation.)
• If pages are renamed or removed, have all internal links to those pages been fixed?
• If pages are added, have they been linked to or placed in the menu?
• Did the PR receive at least one approval from a committer, and all issues raised have been addressed?

[seth-shaw-unlv]

The note about creating a profile via the twig templating system predates the metadata map plugins; I would scratch that. I would also move the note about the metatag plugin into the "OAI-DC Metadata Format/Metadata Mappings" section as the RDF and Metatag plugins are both ways of getting defining OAI-DC.

[jordandukart]

Not sure the best way to present / convey this for documentation but a lot of the default rest_oai_pmh conventions expect a very flat render array style of fields to be returned when implementing transformRecord() unless you are really going to go off the beaten path with introducing a custom twig template or build method.

Guess tl;dring the above would be the default processes expect a flat array of fields to be returned?

[kspurgin]

Yeah, I think anyone with any experience writing any code for Islandora will get the drift. I feel like I even ran into this basic idea writing field display stuff for I7. Tweaked the wording a bit.

[kspurgin]

Feedback incorporated.

[ysuarez]

@kspurgin, speaking on behalf of DIG, are you planning on making changes do this PR, are you waiting for someone to review, or do you need any help from DIG to get this merged into the documentation? Just trying to help. Thanks in advance.

[kspurgin]

Thanks for checking in, @ysuarez.

I don't plan on making any more changes unless further changes are requested. I believe I incorporated all existing feedback from @seth-shaw-unlv and @jordandukart

[seth-shaw-unlv]

👍