This commit adds support for HTTP/3 and QUIC under a disabled-by-default
feature `http3-preview`. The current implementation depends on modified
versions of h3 and s2n-quic-h3 which will need to be upstreamed and
published before a release is possible.
During the course of development various facets of Rocket's internal
connection handling and recent listener APIs were improved. The complete
list of changes included in this PR is:
* A `shutdown` module was introduced.
* `config::Shutdown` was renamed to `ShutdownConfig` and moved to
`shutdown` while being re-exported from `config`.
* `ListenerAddr` is now called `Endpoint`. Various methods which
previously referred to "addresses" now refer to "endpoints".
* `Rocket::endpoint()` was renamed to `Rocket::endpoints()` and now
returns an iterator over the endpoints Rocket is listening on.
* `Endpoint` acquired various query utility methods.
* The `{set_}remote()` methods now take/produce `Endpoint`s.
* `TlsBindable` only accepts single-phase internal interfaces.
* Bind error messages include candidate endpoint info when possible.
* The warning message when a secret key is not configured now includes
information about its effect on private cookies.
Internal changes include:
* Config module tests were moved to `config/tests.rs`.
* The cancellable I/O implementation was significantly simplified.
* The `TripWire` implementation was simplified.
* Individual shutdown stages can now be awaited on via `Stages`.
* The `Shield` implementation was simplified.
Resolves#2723.
Sergio Benitez
Nya