Implement caching for citation relations

[koppor]

Context

PR #10980 introduced a memory saving for citation relations to prevent JabRef's memory usage growing constantly. The drawback is that citation relations might become unavailable due to API limitations of the online service.

Quoting https://libguides.ucalgary.ca/c.php?g=732144&p=5260798

The API allows up to 100 requests per 5 minutes. To access a higher rate limit, complete the form to request authentication for your project.

That means, for a large library, I cannot step through the references, because I could hit the rate limit. I know, this is seldom, but it could happen at following setting: In a corporate setting: all requests are going through a proxy. Thus, the rate limit is not per person, but per the SUM of persons. In case 100 researchers work in parallel with JabRef, each researcher can get ONE request per 5 minutes. And per entry TWO requests are needed: For the citing and the cited by.

The following solution would really help to make the citation relations really usable. (Because the information for each DOI is stored independent of each library and is presented as soon it is availbable.)...

Task 1

Let's investiage MVStore. MVStore is a library storing the values of a hashmap on disk. Thus, NOT in memory. Thus, it takes less memory than a full hash map in memory, because it is on disk. -- MVStore routes through the request to a map entry to disk. - See https://www.h2database.com/html/mvstore.html for details.

Estimate: 100 lines of code, but scattered around JabRef. NativeDesktop needs to be touched etc. The most difficult thing will be the closing of the MVStore. Since the DOIs are globally unique, one can close the MVStore when JabRef is shut down. This makes it "easier" (in comparison to #10937, where for each tab some closing thing were necessary). -- Nevertheless, it could be that this will be a back-and-forth code development (meaning: code reviews with significant changes could come up).

Implementation hint: Do NOT do it like org.jabref.logic.journals.JournalAbbreviationRepository, because there, there is no direct access to the MVStore, but new hashmaps are created. We really need to work on the Maps provided by the MVStore. Because the MVStore "intelligent" does memory management.

Task 2

Follow-up requirement: Refresh the DOI information if one week passed since the last fetch. Maybe this can be baked into the HashMap designed for the MVStore.

[rohit-garga]

Hey @koppor, I would like to take this up

[github-actions]

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