approvals: remove post undelete endpoint.

Remove `POST /moderator/post/undelete` endpoint. Replace it with
`POST /post_approvals` instead.

Fixes it so that undeleting a post has the same behavior as approving a
post. Namely, it reloads the page instead of just flashing a "Post was
undeleted" message.

test/functional/moderator/post/posts_controller_test.rb

@@ -35,20 +35,6 @@ module Moderator
           end
         end
 
-        context "undelete action" do
-          should "render" do
-            as_user do
-              @post.update(is_deleted: true)
-            end
-            assert_difference(-> { PostApproval.count }, 1) do
-              post_auth undelete_moderator_post_post_path(@post), @admin, params: {:format => "js"}
-            end
-
-            assert_response :success
-            assert(!@post.reload.is_deleted?)
-          end
-        end
-
         context "confirm_move_favorites action" do
           should "render" do
             get_auth confirm_ban_moderator_post_post_path(@post), @admin

test/functional/post_approvals_controller_test.rb

@@ -7,12 +7,24 @@ class PostApprovalsControllerTest < ActionDispatch::IntegrationTest
     end
 
     context "create action" do
-      should "render" do
-        @post = create(:post, is_pending: true)
-        post_auth post_approvals_path(post_id: @post.id, format: :js), @approver
+      context "for a pending post" do
+        should "approve the post" do
+          @post = create(:post, is_pending: true)
+          post_auth post_approvals_path(post_id: @post.id, format: :js), @approver
 
-        assert_response :success
-        assert(!@post.reload.is_pending?)
+          assert_response :success
+          assert(!@post.reload.is_pending?)
+        end
+      end
+
+      context "for a deleted post" do
+        should "undelete the post" do
+          @post = create(:post, is_deleted: true)
+          post_auth post_approvals_path(post_id: @post.id, format: :js), @approver
+
+          assert_response :success
+          assert(!@post.reload.is_deleted?)
+        end
       end
     end