Use nlohmann json as external dependency

Author: zerodefect

.gitignore

@@ -1,2 +1,10 @@
 /deps/
 /build/
+
+#CLion-created directories.
+/cmake-build-debug/*
+/cmake-build-release/*
+/cmake-build-minsizerel*
+/cmake-build-relwithdebinfo*
+
+/.idea/*

CMakeLists.txt

@@ -1,15 +1,21 @@
-cmake_minimum_required(VERSION 3.0)
+cmake_minimum_required(VERSION 3.16)
 
 project(sdptransform VERSION 1.2.10)
 
-# For CMake >= 3.1.
-set(CMAKE_CXX_STANDARD 14)
-set(CMAKE_CXX_STANDARD_REQUIRED ON)
-set(CMAKE_CXX_EXTENSIONS OFF)
-# For CMake < 3.1.
-add_compile_options(-std=c++14)
+set(CMAKE_CXX_STANDARD 17)
 
-add_subdirectory(test readme-helper)
+option(BUILD_TESTS "Build unit tests" OFF)
+option(BUILD_UTILS "Build utility applications" OFF)
+
+find_package(nlohmann_json 3.11.3 REQUIRED)
+
+if (${BUILD_TESTS})
+    add_subdirectory(test)
+endif()
+
+if (${BUILD_UTILS})
+    add_subdirectory(utils)
+endif()
 
 include_directories(${sdptransform_SOURCE_DIR}/include)
 
@@ -24,10 +30,10 @@ set(
 set(
 	HEADER_FILES
 	include/sdptransform.hpp
-	include/json.hpp
 )
 
 add_library(sdptransform STATIC ${SOURCE_FILES})
+target_link_libraries(sdptransform PRIVATE nlohmann_json::nlohmann_json)
 
 install(TARGETS sdptransform DESTINATION lib)
 install(FILES ${HEADER_FILES} DESTINATION include/sdptransform)