Correct super delegation in model hooks

Sequel expects super to be called *last* in `before` hooks and *first*
in `after` hooks. The only exception to this rule seems to be when we
need to detect changed columns in `after_save` hooks since the `dirty`
plugin clears its state in `after_save`.

[#68919544]

Signed-off-by: Joseph Palermo <jpalermo@pivotallabs.com>
Move AppUsageEvent creation for App into after_create and after_update

- Allows us to use the Sequel standard of calling super first in after_*

[#68919544]

Signed-off-by: Joseph Palermo <jpalermo@pivotallabs.com>