Fix #4982: Add route to remove a post from a favorite group

app/controllers/favorite_groups_controller.rb

@@ -59,4 +59,12 @@ class FavoriteGroupsController < ApplicationController
 
     respond_with(@favorite_group)
   end
+
+  def remove_post
+    @favorite_group = authorize FavoriteGroup.find(params[:id])
+    @post = Post.find(params[:post_id])
+    @favorite_group.remove(@post)
+
+    respond_with(@favorite_group)
+  end
 end

app/policies/favorite_group_policy.rb

@@ -17,6 +17,10 @@ class FavoriteGroupPolicy < ApplicationPolicy
     update?
   end
 
+  def remove_post?
+    update?
+  end
+
   def can_enable_privacy?
     record.creator.is_gold?
   end

app/views/favorite_groups/remove_post.js.erb

@@ -0,0 +1,7 @@
+<% if @favorite_group.errors.any? %>
+  Danbooru.notice("<%= j @favorite_group.errors.full_messages.join("; ") %>");
+<% else %>
+  Danbooru.notice("Removed post from favorite group <%= j @favorite_group.pretty_name %>");
+<% end %>
+
+$("#add-to-favgroup-dialog").dialog("close");