S2: add viewer_is_maintainer()

[ex_uniquewo]

Title
S2: add viewer_is_maintainer()

Short, concise description of the idea
I'd like to have some elements of the sidebar only visible to my co-maintainers in order to create an admin tools box.

Full description of the ideaviewer_is_owner() lets you have private elements in one's paid journal but it doesn't work in communities. Either make it work

Comments

[turlough]

Excellent suggestion!

[ursamajor]

Sure, this makes sense!

[ceilidh]

Yes please!

[foxfirefey]

This would be nice.

[hakeber]

Absolutely!