Generate an entry from ID

[colinhex]

Fixes #4183

Adds new code segment in JabrefFrame to handle a new popover.
Adds multiple new files:

• CompositeIdFetcher.java, logic to try all IdFetchers
• GenerateEntryFromIdDialog.java, acting as fxmlController for...
• GenerateEntryFromIdDialog.fxml, javafx gui for within the new popover
• GenerateEntryFromIdAction.java, wraps fetching the entry in an action
• CompositeIdFetcherTest.java

• Change in CHANGELOG.md described in a way that is understandable for the average user (if applicable)
• Tests created for changes (if applicable)
• Manually tested changed features in running JabRef (always required)
• Screenshots added in PR description (for UI changes)
• Checked documentation: Is the information available and up to date? If not, I created an issue at https://github.com/JabRef/user-documentation/issues or, even better, I submitted a pull request to the documentation repository.

[tobiasdiez]

Thanks for your work. Some suggestions from my side about the general code structure / flow.

[koppor]

Some small code comments

[calixtus]

I like that feature very much. Thank you for adressing the remaining issues. Looks good to me!

[koppor]

Small nitpick comments remain 😇

[koppor]

Since a few hours, I am working with the feature, and it works great. One micro thing, then it is good to go from my side

[koppor]

In case an entry already exists ...

... and error is thrown

Is it possible to display "Entry already exists"?

Test DOI: https://doi.org/10.1016/j.infsof.2014.03.009

[koppor]

When an error occurs, the error should be included in the error message somehow. Maybe reuse the FetcherException things?

https://doi.org/10.1109/VISSOFT52517.2021.00013 always leads to the error popup.

OK, it is an invalid DOI. Maybe, the error message can be routed to the user?

[colinhex]

I've included the exception messages in the update-messages of the background-task, now it gives more specific feedback.

[koppor]

l10n consistency test

org.opentest4j.AssertionFailedError: Obsolete keys found in language properties file:

Entry could not be created

1. CHECK IF THE KEY IS REALLY NOT USED ANYMORE
2. REMOVE THESE FROM THE ENGLISH LANGUAGE FILE
   ==> expected: <[]> but was: <[Entry could not be created]>

[Siedlerchr]

Yeah! This looks good now 🥇 Thanks for the patience and I hope we didn't annoy you with our nitpicking :)