Various fixes and improvements (#12878)

* Fix unused role routes being generated

* Remove unused JavaScript code

* Refactor filters code to be DRYer

* Fix `.count == 0` comparisons to `.empty?` in views

* Fix filters in views

app/controllers/relationships_controller.rb

@@ -85,7 +85,7 @@ class RelationshipsController < ApplicationController
   end
 
   def current_params
-    params.slice(:page, :status, :relationship, :by_domain, :activity, :order).permit(:page, :status, :relationship, :by_domain, :activity, :order)
+    params.slice(:page, *RelationshipFilter::KEYS).permit(:page, *RelationshipFilter::KEYS)
   end
 
   def action_from_button