Move read_only posts to its own endpoint, to correctly sort by PostActions

[dessalines]

Requirements

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Is your proposal related to a problem?

As I'm working on cursor pagination in #5429, I'm realizing that its not a good idea to try to include read only posts into list_posts, because it uses a sort key from a different table. It uses post_actions_keys::read to sort, whereas every other one uses the Post table keys.

Similar to liked_only, it should be extracted to its own endpoint, with a predictable order, and none of the filters.

Describe the solution you'd like.

Create a post/read/list endpoint, which uses a proper post_actions::read sort.

Describe alternatives you've considered.

NA

Additional context

#4499
#5429

[dullbananas]

The type of action to list posts for (read, like, etc) should be a query parameter

[Nutomic]

Why does it matter which table the sort key is from? Anyway the parameters get passed into PostQuery, so it should work fine with the same endpoint.

[dessalines]

I'm in the process of cleaning up post_view.rs which is a complete mess right now, and because we've tried to make it too versatile, we have a lot of overly complicated cases where the sorting column(s) change based on these params. I'm restricting and cleaning this up so that it can only do front page sorts / feeds. To get into the details, building a cursor for post_actions requires putting a lot of extra info in the cursor, which isn't necessary if I only restrict this cursor to a Post, which contains all the necessary sorting keys.

PostQuery / list_posts should now only be used for pulling front page or community feeds.

I've removed / moved a bunch of its functionality to other endpoints anyway, so this is just part of that cleanup.

• saved_only is removed, and is now at account/auth/saved
• listing content by person got moved to person/content
• I'm going to remove search_term, because post searching is now moved to search
• I'm going to remove liked_only to its own combined endpoint, which includes liked comments
• I'm going to move read_only to its own endpoint also, which only sorts by post_actions::read

[dessalines]

I'd also like to note that this only has to do with ordering the posts by read.

PostQuery already has a show_read param, that can be used to hide read posts, but doesn't affect the ordering.

These were confusingly overlapping anyway.

[dessalines]

Comes after #4606