Allow list for "when" parameter

[rsinger86]

In my projects, it's been a little cumbersome to stack decorators when you want to react to multiple fields changing:

    @hook("after_update", when="published", has_changed=True)
    @hook("after_update", when="path", has_changed=True)
    @hook("after_update", when="type", has_changed=True)
    def handle_update(self):
        # do something

I see a couple of ways to handle this:

Option 1:

    @hook("after_update", when=["type", "path", "published"], has_changed=True)
    def handle_update(self):
        # do something

Option 2:

    @hook("after_update", when_any=["type", "path", "published"], has_changed=True)
    def handle_update(self):
        # do something

Option 2 would enable adding a when_all parameter later on if we want to get a little fancy with boolean logic. On the other hand, maybe it's best to keep this simple - nothing wrong with stacking decorators. Any feedback would be appreciated.

[simkimsia]

I vote for when_any

[rsinger86]

@simkimsia - this is in the latest release. Thanks for your input!