Make approval queue reasons hookable

[Colonel_mortis]

I have my own hooks to add additional spam filter rules, and I imagine I'm not alone. I want them to be able to take advantage of showing the reason that the post got mod queued, but there's no easy way to do that, because the post ID is only available after it's saved, and there's no suitable hook point in \IPS\Content::checkProfanityFilters between saving and constructing the approval entry.

It would make me much happier if you replaced the switch statement on line 773 with either:

• A method call that we can hook
• Or fall back to setting $log->held_data = ["match" => $filtersMatched["match"]]
• Or just always do that, and drop the logic to choose between the cases entirely

You already made Approval itself hookable by pulling availableReasons out into a method (though why it's necessary to have it at all is a bit confusing to me), so this feels like an unfortunate oversight.

I believe the image hold log in \IPS\Content::shouldTriggerProfanityFilters on line 639-643 is also going to hit the issue with the post ID not being available yet, but I obviously don't pay enough to be able to test that. The changes suggested here should make that code easier to unify with the rest of the cases.