task/FP-982: Add rebuild_index haystack signal processor

[rstijerina]

Overview

On a document publish, unpublish, or delete event, we want the cms index to rebuild. This adds a new signal processor that hooks into Haystack, and subclasses the BaseSignalProcessor class.

Notes:

An improvement would be to add/remove the document from the index instead of rebuilding, but I had trouble updating the index with the instance object returned from the post_publish signal. Since we have relatively few documents and activity on each cms, the occasional rebuild_index call will not be a resource burden.

Testing:

1. Load the cms locally, and add an unpublished document.
2. Curl localhost:9201/cms-dev-cms/_search and verify the document is not in the index
3. Publish the document, curl localhost:9201/cms-dev-cms/_search, and verify the document is now there
4. Unpublish or delete the document, curl localhost:9201/cms-dev-cms/_search, and verify the document is gone

[wesleyboar]

Elegant.

Testing

• ✓ Confirm index did not auto-update on main.
• ✓ Confirm publish of edited page updates index.
  • "Text" plugin addition
  • "Text" plugin change
• ✓ Confirm page removal updates index.
• ✓ Confirm page addition (after publish) updates index.

[wesleyboar]

I don't want to nitpick, but at least let Bob McNewguy know this is search-related. A haystack signal process who what, now? I get it, but I sure didn't used to.

[wesleyboar]

Thank you for mentioning search!