* DEV: Sanitize HTML admin inputs
This PR adds on-save HTML sanitization for:
Client site settings
translation overrides
badges descriptions
user fields descriptions
I used Rails's SafeListSanitizer, which [accepts the following HTML tags and attributes](018cf54073/lib/rails/html/sanitizer.rb (L108))
* Make sure that the sanitization logic doesn't corrupt settings with special characters
When the admin creates a new custom field they can specify if that field should be searchable or not.
That setting is taken into consideration for quick search results.
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
Rails yanked out observers many many years ago, instead the functionality
was yanked out to a gem that is very lightly maintained.
For example: if we want to upgrade to rails 5 there is no published gem
Internally the usage of observers had quite a few problem.
The series of refactors renamed a bunch of classes to give us more clarity
and removed some magic.
