AppVeyor build VMs should provide at least two cores. Parallelize builds
and tests.
In addition, enable output on failure and disable verbose test output.

Restore the previously disabled check for regression #3070 on all
compilers but MSVC.

To summarize the issue:
Given namespace fs = std::filesystem.
On MSVC attempting to construct an fs::path from json results in an
ambiguous overload resolution because fs::path can be constructed from
both a std::string as well as another fs::path.
To the best of my knowledge there is no way to fix an ambiguous overload
situation involving a type we do not control and with json implicitly
converting to both std::string and fs::path.

Re-enabling the check where it compiles and keeping it disabled for MSVC
is the best we can do.

Closes #3377 and #3382.

* Report the right __cplusplus value for MSVC in basic_json meta()

* Run amalgamate

* Avoid clash with Arduino defines

* Arduino defines B0/B1 in "binary.h"
     #define B0 0
     #define B1 1
  This clashes with names of the template
  variables in conjuction

* Renaming them to "B" rather than "B1"
  Now it can be used as-is in Arduino projects

* Apply suggestions from code review

* Apply suggestions from code review
Co-authored-by: NDaniel Ansorregui <d.ansorregui@samsung.com>
Co-authored-by: NNiels Lohmann <niels.lohmann@gmail.com>

* Refactor assertion and adjust expected error message

* Refactor assertion and adjust expected error message

* Refactor assertion and remove redundant local variable

* Refactor assertion and remove redundant local variable

* Rename local variable

* Apply formatting

* Add missing check

* Refactor assertions in unit-algorithms.cpp

* Refactor assertions in unit-bson.cpp

* Refactor assertions in unit-cbor.cpp

* Refactor assertions in unit-class_const_iterator.cpp

* Refactor assertions in unit-class_iterator.cpp

* Refactor assertions in unit-class_parser.cpp

* Refactor assertions in unit-constructor1.cpp

* Refactor assertions in unit-convenience.cpp

* Refactor assertions in unit-conversions.cpp

* Refactor assertions in unit-deserialization.cpp

* Refactor assertions in unit-element_access1.cpp

* Refactor assertions in unit-element_access2.cpp

* Refactor assertions in unit-iterators1.cpp

* Refactor assertions in unit-iterators2.cpp

* Refactor assertions in unit-json_patch.cpp

* Refactor assertions in unit-json_pointer.cpp

* Refactor assertions in unit-modifiers.cpp

* Refactor assertions in unit-msgpack.cpp

* Refactor assertions in unit-reference_access.cpp

* Refactor assertions in unit-regression1.cpp

* Refactor assertions in unit-serialization.cpp

* Refactor assertions in unit-ubjson.cpp

* Refactor assertions in unit-unicode1.cpp

* Apply formatting

* Refactor unit test creation

Add functions for creating tests and to supply test- and
standard-specific build settings.

Raises minimum CMake version to 3.13 in test directory.

json_test_add_test_for(
    <file>
    MAIN <main>
    [CXX_STANDARDS <version_number>...] [FORCE])

Given a <file> unit-foo.cpp, produces

    test-foo_cpp<version_number>

if C++ standard <version_number> is supported by the compiler and
thesource file contains JSON_HAS_CPP_<version_number>.  Use FORCE to
create the test regardless of the file containing
JSON_HAS_CPP_<version_number>.  Test targets are linked against <main>.
CXX_STANDARDS defaults to "11".

json_test_set_test_options(
    all|<tests>
    [CXX_STANDARDS all|<args>...]
    [COMPILE_DEFINITIONS <args>...]
    [COMPILE_FEATURES <args>...]
    [COMPILE_OPTIONS <args>...]
    [LINK_LIBRARIES <args>...]
    [LINK_OPTIONS <args>...])

Supply test- and standard-specific build settings.
Specify multiple tests using a list e.g., "test-foo;test-bar".

Must be called BEFORE the test is created.

* Use CMAKE_MODULE_PATH

* Don't undef some macros if JSON_TEST_KEEP_MACROS is defined

* Use JSON_TEST_KEEP_MACROS

Incidentally enables the regression tests for #2546 and #3070.

A CHECK_THROWS_WITH_AS in #3070 was disabled which is tracked in #3377
and a line in from_json(..., std_fs::path&) was marked with LCOV_EXCL_LINE.

* Add three-way comparison feature test macro

* Disable broken comparison if JSON_HAS_THREE_WAY_COMPARISON

* Fix redefinition of inline constexpr statics

Redelcaration of inline constexpr static data members in namespace scope
was deprecated in C++17. Fixes -Werror=deprecated compilation failures.

* Fix more test build failures due to missing noexcept

* CI: update cmake_flags test to use CMake 3.13 in test directory

Also change default for JSON_BuildTests option to depend on CMake
version.

* CI: turn *_CXXFLAGS into CMake lists

* CI: use JSON_TestStandards to set CXX_STANDARD

* CI: pass extra CXXFLAGS to standards tests

Commit f28fc226 introduced const qualifiers on post-(inc-/dec-)rement
operators of iterators. These qualifiers prevent the use of basic_json
in place of std::ranges::range, which requires the post-increment
operator to be equality-preserving.

These changes appear to be the result of ICC compiler suggestions, and
no further explanation is discernible from the PR discussion (#858).
Further testing revealed, that clang-tidy also suggests adding const to
prevent "accidental mutation of a temporary object".

As an alternative, this commit partially reverts f28fc226, removing all
added const qualifiers from return types and adds lvalue reference
qualifiers to the operator member functions instead.

Unit tests ensure the operators remain equality-preserving and
accidental mutation of temporaries following post-(inc-/dec-)rement is
prohibited.

Fixes #3331.

* 🔧 use proper GCC binary

* 🔧 add more GCC warning flags

* ⚗ try fix from https://github.com/nlohmann/json/issues/3138#issuecomment-1015562666

* Fix custom allocator test build failures (C++20)

Allocator tests fail to compile in C++20 mode with clang+MS STL due
to missing copy constructors.

* Fix test build failures due to missing noexcept (gcc-12)

* alt_string has multiple member functions that should be marked noexcept.
* nlohmann::ordered_map constructors can be noexcept.

Compilation failures result from the warning flag -Werror=noexcept and
gcc-12.

* Disable broken comparison tests in C++20 mode
Co-authored-by: NNiels Lohmann <mail@nlohmann.me>

* Update macros.md

Typos, typos

One of the ordered_map constructors was incorrectly accepting a
std::initializer_list<T> instead of std::initializer_list<value_type>.

Add regression test.

Fixes #3343.

* 🔧 use FetchContent_MakeAvailable

* 💚 fix test names

* CI: add workflow_dispatch trigger

* CI: change msvc2019*/clang* runners to windows-2019

GitHub updated their runners. windows-latest is now based on Windows
Server 2022 and comes with different tool versions.
MSVC 2019 is still available via the windows-2019 runner.

* Update CITATION.cff cffversion to 1.2.0

* Fix CITATION.cff date-released
Co-authored-by: NAbel Soares Siqueira <abel.s.siqueira@gmail.com>

* Added new macros NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT and NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT.

* Updated docs for NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT and NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT accordingly

* Rephrased docs for NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT and NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT

* Updated docs for NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT and NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT

* Renamed default_obj in to avoid name clashes

* Added test for serialization of default constructed object

* Add const to getters for macro tests
Co-authored-by: NChaoya Li <harry75369@gmail.com>

* .github/workflows/windows.yml: Add support for Visual Studio 2022

This is available in github actions since some time now [1].

[1]: https://github.com/actions/virtual-environments/issues/3949

* README.md: Add VS 2022 [skip ci]

The version and the build engine version (aka MSBuild version) were
taken from [1].

[1]: https://github.com/actions/virtual-environments/blob/win22/20220116.1/images/win/Windows2022-Readme.md

* 🔨 add script to create xz archive