Bug 33716: Preparation

Bug 33716: Preparation

New Illrequest::Workflow superclass
New Illrequest::Workflow::TypeDisclaimer
Moved Illrequest::Availability to Illrequest::Workflow::Availability

Removed check for backend capability "should_display_availability"
Instead, the check is now done for "can_create_request" backend
capability
This serves the purpose of having the backend let core know
if it can create the request or not. In other words, if the
create form has been submitted or not.

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>