allow editors to mark a revision/suggestion as minor

[cellio]

Purely as an informational matter, can we allow edits and suggested edits to be marked as minor? This would not change any workflows or bumping, though it could be a first step to such changes in the future. I'm envisioning:

• add a checkbox on the edit page for "this is a minor edit" (JIT help for what's minor could go here)
• if it's a suggested edit, show that on the review page too and allow the reviewer to toggle it (reviewers can edit revision comments already; suggested edits are not immutable)
• in the post history, indicate that an edit was minor if it was (use case: don't want to bother to expand the diff and dig through it for a typo)

While a minimal implementation that doesn't change the schema would be possible if a little fragile (add the checkbox/button/whatever and use it to change the revision comment, for example), I suspect it would be better to actually record this flag in the database from the start (a new is_minor column, maybe). This will allow us to use the information in the future.

(Suggested in a discussion on the community server. I'm sure it's come up on meta too but don't have links right now.)

[trichoplax]

Should moderators and/or curators be able to amend this flag after the edit has been saved?

That is, if a suggester and approver agree that an edit is minor, but later it is decided that this was the wrong decision, should there be a way for someone to fix this so the edit no longer shows as minor?

[cellio]

Should moderators and/or curators be able to amend this flag after the edit has been saved?

I think so, though maybe handle in tandem with #1543? We want curators to be able to modify problematic edit comments, and modifying incorrect minor-edit flags feels like it fits in with that. Probably this means "for people with the ability, make fields on the post history editable", but let's figure out the approach we want and then do both.