[Mediawiki-api] Write API should be restricted to logged-in users only

[Max Semenik]

API is intended for bots, not humans. Making it accept anon edits just
allows bots to edit accidentally logged off. And the AssertEdit
extension doesn't seem to work for API. What can be done about this?

Simply adding an AlternateEdit hook call to ApiEditPage leads to ugly
HTML output.

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  Max Semenik ([[User:MaxSem]])