Enhancing how we store and relate all ActivityPub data

[Menrath]

We figured out in #622 that we need a place to collect all proposals directed at changing how we store all ActivityPub related data:

The following are just thoughts. I am not an expert on MySQL or WordPress database queries. Please speak up against any suggestion if you know arguments against it.

Proposals/Ideas:

1. Make use of the post_content_filtered column

1.1. In the posts table to temporary store transformed posts

Seems like that would be a use case for why the column post_content_filtered is there in the first place. The only problem is that there might be conflicts with other plugins that use this column, especially the popular Web Stories plugin that misuses it heavily along with a markdown plugin from Jetpack. The post_content_filtered should always be generated from the post_content, never the other way round. But these two seem the only plugins that I could find that use this column, we sure could built-in a protection for those cases.

1.2. To store the most needed information from the actor object

This would be the inbox.

2. Actors/follow post type: use the post_content column to store the actor object.

Store the latest fetched and validated activity-json representation of the (remote) actor.

3. Abstract all ActivityPub actors to the same table

Either store each actor within a custom post type or generate a WordPress user for each actor.

• Connecting followers and follow requests to the target actor, not the other way round (this is the direction in which we usually query this information).
• Standardize the internal flow across the user-actor, blog-actor, application-actor and future custom actors.