[PATCH 00 of 14] request body discarding cleanup

[Maxim Dounin]

Hello!

The following patch series is focused on various edge cases related
to reading and discarding of a request body.

Notably, it should be now safe (from the request body point of view)
to configure complex processing for errors, such as 413 (Request Entity
Too Large), including proxying, without additional precautions, such
as "proxy_set_header Content-Length '';" and "proxy_pass_request_body off;".

The series also fixes the issue observed with error_page 413 and HTTP/2
(and HTTP/3), which previously required relaxed client_max_body_size
limit in the error page location to work.

Review and testing appreciated.

-- 
Maxim Dounin