adds button for duplicating annotations

[normanrz]

Steps to test:

• Open an annotation (yours or from somebody else)
• Open the menu next to "save", click duplicate
• The current annotation will be saved, a duplicate will be created and you will be redirected to the duplicate

Issues:

• fixes Create Duplicate of Annotation #5570

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(Please delete unneeded items, merge only when none are left open)

• Updated (unreleased) changelog
• Updated documentation if applicable
• Ready for review

[philippotto]

lgtm 👍

[normanrz]

@philippotto Can you think of situations when we don't want to allow duplicating?

[philippotto]

@philippotto Can you think of situations when we don't want to allow duplicating?

no, even if we would forbid it in certain circumstances, downloading+reuploading would be a workaround, anyway (which we don't forbid, either).

[normanrz]

@philippotto Can you think of situations when we don't want to allow duplicating?

no, even if we would forbid it in certain circumstances, downloading+reuploading would be a workaround, anyway (which we don't forbid, either).

Well, there is an allowDownload restriction.

[fm3]

allowDownload is currently always identical to allowAccess