The code for listing all of the defined queries is mixed together with the code for editing a single query. Notably, this results in large amounts of unnecessary data being loaded for the list view, which causes substantial rendering slowdowns.
To address this issue, we now only load the necessary data for the list view, and load the full data when it's actually needed (any endpoint that returns a single query). The primary changes that achieve this are:
- Create a new `QueryDetailsSerializer` serialiser, which includes all of the query info, and change the existing `QuerySerializer` serialiser to only include the necessary attributes of each query for generating a list of them all.
- Split the monolith `/plugins/explorer` route into `/plugins/explorer` for showing just the list of queries, and `/plugins/explorer/queries/:query_id`, for showing/editing/running a specific query.
This commit updates the plugin to the latest guidelines, as shown in
discourse-plugin-skeleton, which involves moving a lot of the code to
dedicated files, use proper namespaces, use the autoloader as much as
possible, etc.
