autopkgtest is flaky and sometimes fails even if the code is completely
fine. When it crashes like this, it exits with code 16.

With this change
all CI runs that exit with code 16 won't be considered failures, but
will just report a warning.

For more info, see `man autopkgtest`

Move the Http client to `Pistache::Experimental`

`chmod +x .hooks/pre-commit`

Cleanups

Closes #952. To be merged after #955

Nested namespaces in serializer/rapidjson.h and client.cc, reformat all
files, add .clang-format-ignore ignoring subprojects, use angled
brackets when including gtest.h.

Huge diff because of whitespace changes

Fix serializer install and remove unneeded prefix

Fixes #950

Add support for multiple archs in autopkgtest CI

This took **a lot** of time, as autopkgtest-build-qemu has been able to
build non-x86 for less than a release (version 5.17, unreleased),
and it isn't meant to be (easly) used on Ubuntu (and unfortunately GH
Actions only support Ubuntu).

This is extremely fragile; adding a CPU core breaks something, adding a
MB of RAM breaks something, installing recommended packages breaks
something... you get it. But it works. Beautiful, isn't it?

This currently tests amd64, arm64. armhf, i386 and ppc64el. s390x seems
unsupported by autopkgtest-build-qemu.

If you're curious to see how many trials it took, have a look at this
test branch:
github.com/Tachi107/pistache/tree/actions-autopkgtest-multiarch-test

Bump prismjs from 1.23.0 to 1.24.0 in /pistache.io

Bumps [prismjs](https://github.com/PrismJS/prism) from 1.23.0 to 1.24.0.
- [Release notes](https://github.com/PrismJS/prism/releases)
- [Changelog](https://github.com/PrismJS/prism/blob/master/CHANGELOG.md)
- [Commits](https://github.com/PrismJS/prism/compare/v1.23.0...v1.24.0)

---
updated-dependencies:
- dependency-name: prismjs
  dependency-type: indirect
...
Signed-off-by: dependabot[bot] <support@github.com>

Add autopkgtest GitHub Action

This CI workflow builds and tests every commit and PR using autopkgtest.
It builds a Debian Testing image using autopkgtest-build-qemu
(autopkgtest-buildvm-ubuntu-cloud was too slow), builds the source
package and test is with autopkgtest.

I'm trying to set this up for multiple architectures (see
https://github.com/Tachi107/pistache/tree/actions-autopkgtest), but for
whatever reason Ubuntu's autopkgtest-build-qemu is unable to build
images for foreign architectures, as it fails with
"E: Unable to locate package linux-image-arm64", while it should be
downloading it from
https://packages.debian.org/testing/linux-image-arm64.

If you know how to help please let me know.

Remove --no-tests option when preparing tarballs

The option was added in Meson 0.550, but we target Meson 0.50

Move copyright notices down the title in docs

Otherwise Docusaurus can't see the document's title

Make Pistache REUSE compliant

Reuse is a specification that aims at making licensing of open source
software easier. You basically have to include an SPDX header in all
files, and when this isn't possible you create a file named
filename.license containing the header. While I find this a bit too much
this is also the only way of reliably determining the license and the
copyright holder of a certain file.

The use of SPDX tags has been adopted by projects like the Linux Kernel
(torvalds/linux/commit/a61127c2130236168321cc76c5a58e15c00ad154),
systemd, etc, and I find it way better that including a long copyright
notice on top of every file.

I didn't add any email address, but if you'd like to it is completely
possible to add them in the SPDX-FileCopyrightText tag, between angle
brackets.

The specification is available on https://reuse.software

Make date.h and cpp-httplib proper dependencies

New connections can come from either IPv4 or IPv6 addresses. Hence, use
a sockaddress structure that can handle both.

Bumps [normalize-url](https://github.com/sindresorhus/normalize-url) from 4.5.0 to 4.5.1.
- [Release notes](https://github.com/sindresorhus/normalize-url/releases)
- [Commits](https://github.com/sindresorhus/normalize-url/commits)

---
updated-dependencies:
- dependency-name: normalize-url
  dependency-type: indirect
...
Signed-off-by: dependabot[bot] <support@github.com>

If someone is building Pistache from source as a subproject they are not
going to commit any changes from there, and setting up the pre-commit
hook is pointless.
It is now also optional, since git is not stictly needed to build the
library, and if you don't have git installed you are probably not going
to commit.

Otherwise Debian packaging wouldn't be possible.

listener: use sockaddr_storage for socket addrs

Update Docusaurus to beta 0

Bump normalize-url from 4.5.0 to 4.5.1 in /pistache.io

Bumps [normalize-url](https://github.com/sindresorhus/normalize-url) from 4.5.0 to 4.5.1.
- [Release notes](https://github.com/sindresorhus/normalize-url/releases)
- [Commits](https://github.com/sindresorhus/normalize-url/commits)

---
updated-dependencies:
- dependency-name: normalize-url
  dependency-type: indirect
...
Signed-off-by: dependabot[bot] <support@github.com>

New connections can come from either IPv4 or IPv6 addresses. Hence, use
a sockaddress structure that can handle both.

They were previously embedded in the source tree, and are now proper
subprojects.
I've also moved rapidjson.h out of include/pistache/thirdparty since it
is part of Pistache - this is a breaking change.