Dynamically check `:admin_*` ability in IssuableBaseService

Closes #2092

app/services/issuable_base_service.rb

@@ -27,8 +27,10 @@ class IssuableBaseService < BaseService
       old_branch, new_branch)
   end
-  def filter_params
-    unless can?(current_user, :admin_issue, project)
+  def filter_params(issuable_ability_name = :issue)
+    ability = :"admin_#{issuable_ability_name}"
+
+    unless can?(current_user, ability, project)
       params.delete(:milestone_id)
       params.delete(:label_ids)
       params.delete(:assignee_id)

app/services/issues/base_service.rb

@@ -10,6 +10,10 @@ module Issues
     private
+    def filter_params
+      super(:issue)
+    end
+
     def execute_hooks(issue, action = 'open')
       issue_data = hook_data(issue, action)
       issue.project.execute_hooks(issue_data, :issue_hooks)

app/services/merge_requests/base_service.rb

@@ -20,5 +20,11 @@ module MergeRequests
         merge_request.project.execute_services(merge_data, :merge_request_hooks)
       end
     end
+
+    private
+
+    def filter_params
+      super(:merge_request)
+    end
   end
 end