Allow parameters for group and username filters on directory (#5815)

app/controllers/directory_items_controller.rb

@@ -10,6 +10,14 @@ class DirectoryItemsController < ApplicationController
 
     result = DirectoryItem.where(period_type: period_type).includes(:user)
 
+    if params[:group]
+      result = result.includes(user: :groups).where(users: {groups: {name: params[:group]}})
+    end
+
+    if params[:exclude_usernames]
+      result = result.references(:user).where.not(users: {username: params[:exclude_usernames].split(",")})
+    end
+
     order = params[:order] || DirectoryItem.headings.first
     if DirectoryItem.headings.include?(order.to_sym)
       dir = params[:asc] ? 'ASC' : 'DESC'