Remove left joins and use only one call to select method in post_view.rs

[dullbananas]

This makes the code cleaner and might also improve build time because now there's only one call to select.

I will probably make this change to other views in separate pull requests in the future.

[dullbananas]

I will try to get rid of the other left joins

Left join is only useful if there's a possibility of a row on the left side being joined with more than one row on the right

[phiresky]

This is great imo. I was just looking at those queries for #3872 and all those left joins are pretty hard to understand and reason about. This is much easier to read. It will need a bit of testing though to see if the query plans are still the same or better. I think they should be and could even be better because with left joins sometimes postgresql estimates multiple rows being retrieved from the left join.

[phiresky]

it would be great if you could also make it so all those person_id_join things aren't actually called when person_id is null (logged out) instead of calling it with a fake -1 value

[dessalines]

@Nutomic and @phiresky should probably take a look before merging also.

[phiresky]

looks good to me 👍

[dessalines]

nutomic has some comments above too tho.