Activitypub crate rewrite

[Nutomic]

This is finished now. Took some effort to make things work and fix tests. But thanks to previous decoupling of apub and api crates it didnt require any changes in the api crates, otherwise this would have been even more complex.

See the docs for details how the activitypub crate works now: https://docs.rs/activitypub_federation

[Nutomic]

Somehow this change has a very bad effect on compilation time for the lemmy_apub crate, went from 20s to 82s. No idea why, but will try to look into it later.

Edit: based on the output of cargo-llvm-lines there is no difference in the llvm lines being generated, so its not a problem of big macro expansions.

this branch:

cargo llvm-lines -p lemmy_apub | head -20
Lines                  Copies               Function name
-----                  ------               -------------
1425016                41694                (TOTAL)
86237 (6.1%,  6.1%)     55 (0.1%,  0.1%)  diesel_async::pg::AsyncPgConnection::with_prepared_statement::{{closure}}
28050 (2.0%,  8.0%)    110 (0.3%,  0.4%)  diesel_async::stmt_cache::StmtCache<DB,S>::cached_prepared_statement::{{closure}}
17140 (1.2%,  9.2%)     55 (0.1%,  0.5%)  diesel_async::stmt_cache::StmtCache<DB,S>::cached_prepared_statement
16908 (1.2%, 10.4%)     12 (0.0%,  0.6%)  activitypub_federation::activity_queue::send_activity::{{closure}}
16244 (1.1%, 11.5%)     31 (0.1%,  0.6%)  lemmy_apub::insert_activity::{{closure}}
13827 (1.0%, 12.5%)    447 (1.1%,  1.7%)  alloc::boxed::Box<T>::pin
12276 (0.9%, 13.4%)    262 (0.6%,  2.3%)  <serde::de::value::MapDeserializer<I,E> as serde::de::MapAccess>::next_value_seed
12110 (0.8%, 14.2%)    362 (0.9%,  3.2%)  core::result::Result<T,E>::map
11610 (0.8%, 15.0%)     54 (0.1%,  3.3%)  <diesel_async::pg::AsyncPgConnection as diesel_async::AsyncConnection>::load::{{closure}}::{{closure}}
11368 (0.8%, 15.8%)    406 (1.0%,  4.3%)  diesel::query_builder::QueryFragment::is_noop

main branch:

cargo llvm-lines -p lemmy_apub | head -20
Compiling lemmy_apub v0.17.1 (/home/felix/workspace/lemmy/lemmy/crates/apub)
Finished dev [unoptimized] target(s) in 32.62s
warning: the following packages contain code that will be rejected by a future version of Rust: syn v0.14.9, xml5ever v0.16.2
note: to see what the problems were, use the option `--future-incompat-report`, or run `cargo report future-incompatibilities --id 5`
Lines                  Copies               Function name
-----                  ------               -------------
1418548                41314                (TOTAL)
86237 (6.1%,  6.1%)     55 (0.1%,  0.1%)  diesel_async::pg::AsyncPgConnection::with_prepared_statement::{{closure}}
28050 (2.0%,  8.1%)    110 (0.3%,  0.4%)  diesel_async::stmt_cache::StmtCache<DB,S>::cached_prepared_statement::{{closure}}
17140 (1.2%,  9.3%)     55 (0.1%,  0.5%)  diesel_async::stmt_cache::StmtCache<DB,S>::cached_prepared_statement
16674 (1.2%, 10.4%)     12 (0.0%,  0.6%)  activitypub_federation::core::activity_queue::send_activity::{{closure}}
14013 (1.0%, 11.4%)    453 (1.1%,  1.7%)  alloc::boxed::Box<T>::pin
12474 (0.9%, 12.3%)    373 (0.9%,  2.6%)  core::result::Result<T,E>::map
12276 (0.9%, 13.2%)    262 (0.6%,  3.2%)  <serde::de::value::MapDeserializer<I,E> as serde::de::MapAccess>::next_value_seed
11751 (0.8%, 14.0%)     12 (0.0%,  3.2%)  lemmy_apub::activities::send_lemmy_activity::{{closure}}::{{closure}}
11610 (0.8%, 14.8%)     54 (0.1%,  3.4%)  <diesel_async::pg::AsyncPgConnection as diesel_async::AsyncConnection>::load::{{closure}}::{{closure}}
11368 (0.8%, 15.6%)    406 (1.0%,  4.3%)  diesel::query_builder::QueryFragment::is_noop

[dessalines]

Feel free to merge whenever you're ready.