Add sdg manager section to admin

Allow a user to become an sdg manager

app/controllers/admin/sdg/managers_controller.rb

@@ -0,0 +1,23 @@
+class Admin::SDG::ManagersController < Admin::BaseController
+  load_and_authorize_resource instance_name: :sdg_manager, class: "SDG::Manager"
+
+  def index
+    if params[:search]
+      @users = User.accessible_by(current_ability).search(params[:search]).page(params[:page])
+    else
+      @users = User.accessible_by(current_ability).sdg_managers.page(params[:page])
+    end
+  end
+
+  def create
+    @sdg_manager.user_id = params[:user_id]
+    @sdg_manager.save!
+
+    redirect_to admin_sdg_managers_path
+  end
+
+  def destroy
+    @sdg_manager.destroy!
+    redirect_to admin_sdg_managers_path
+  end
+end