Add CMake build and client support

cmake/dev-mode.cmake

@@ -0,0 +1,4 @@
+include(CTest)
+if(BUILD_TESTING)
+  add_subdirectory(test/unit)
+endif()

cmake/install-config.cmake

@@ -0,0 +1,4 @@
+include(CMakeFindDependencyMacro)
+find_dependency(Boost 1.82)
+
+include("${CMAKE_CURRENT_LIST_DIR}/async-mqtt5Targets.cmake")

cmake/install-rules.cmake

@@ -0,0 +1,66 @@
+if(PROJECT_IS_TOP_LEVEL)
+  set(
+      CMAKE_INSTALL_INCLUDEDIR "include/async-mqtt5-${PROJECT_VERSION}"
+      CACHE STRING ""
+  )
+  set_property(CACHE CMAKE_INSTALL_INCLUDEDIR PROPERTY TYPE PATH)
+endif()
+
+# Project is configured with no languages, so tell GNUInstallDirs the lib dir
+set(CMAKE_INSTALL_LIBDIR lib CACHE PATH "")
+
+include(CMakePackageConfigHelpers)
+include(GNUInstallDirs)
+
+# find_package(<package>) call for consumers to find this project
+set(package async-mqtt5)
+
+install(
+    DIRECTORY include/
+    DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}"
+    COMPONENT async-mqtt5_Development
+)
+
+install(
+    TARGETS async_mqtt5
+    EXPORT async-mqtt5Targets
+    INCLUDES DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}"
+)
+
+write_basic_package_version_file(
+    "${package}ConfigVersion.cmake"
+    COMPATIBILITY SameMajorVersion
+    ARCH_INDEPENDENT
+)
+
+# Allow package maintainers to freely override the path for the configs
+set(
+    async-mqtt5_INSTALL_CMAKEDIR "${CMAKE_INSTALL_DATADIR}/${package}"
+    CACHE STRING "CMake package config location relative to the install prefix"
+)
+set_property(CACHE async-mqtt5_INSTALL_CMAKEDIR PROPERTY TYPE PATH)
+mark_as_advanced(async-mqtt5_INSTALL_CMAKEDIR)
+
+install(
+    FILES cmake/install-config.cmake
+    DESTINATION "${async-mqtt5_INSTALL_CMAKEDIR}"
+    RENAME "${package}Config.cmake"
+    COMPONENT async-mqtt5_Development
+)
+
+install(
+    FILES "${PROJECT_BINARY_DIR}/${package}ConfigVersion.cmake"
+    DESTINATION "${async-mqtt5_INSTALL_CMAKEDIR}"
+    COMPONENT async-mqtt5_Development
+)
+
+install(
+    EXPORT async-mqtt5Targets
+    NAMESPACE Async::
+    DESTINATION "${async-mqtt5_INSTALL_CMAKEDIR}"
+    COMPONENT async-mqtt5_Development
+)
+
+if(PROJECT_IS_TOP_LEVEL)
+  include(CPack)
+endif()

cmake/project-is-top-level.cmake

@@ -0,0 +1,6 @@
+# This variable is set by project() in CMake 3.21+
+string(
+    COMPARE EQUAL
+    "${CMAKE_SOURCE_DIR}" "${PROJECT_SOURCE_DIR}"
+    PROJECT_IS_TOP_LEVEL
+)

cmake/variables.cmake

@@ -0,0 +1,28 @@
+# ---- Developer mode ----
+
+# Developer mode enables targets and code paths in the CMake scripts that are
+# only relevant for the developer(s) of async-mqtt5
+# Targets necessary to build the project must be provided unconditionally, so
+# consumers can trivially build and package the project
+if(PROJECT_IS_TOP_LEVEL)
+  option(async-mqtt5_DEVELOPER_MODE "Enable developer mode" OFF)
+endif()
+
+# ---- Warning guard ----
+
+# target_include_directories with the SYSTEM modifier will request the compiler
+# to omit warnings from the provided paths, if the compiler supports that
+# This is to provide a user experience similar to find_package when
+# add_subdirectory or FetchContent is used to consume this project
+set(warning_guard "")
+if(NOT PROJECT_IS_TOP_LEVEL)
+  option(
+      async-mqtt5_INCLUDES_WITH_SYSTEM
+      "Use SYSTEM modifier for async-mqtt5's includes, disabling warnings"
+      ON
+  )
+  mark_as_advanced(async-mqtt5_INCLUDES_WITH_SYSTEM)
+  if(async-mqtt5_INCLUDES_WITH_SYSTEM)
+    set(warning_guard SYSTEM)
+  endif()
+endif()