relay: add "api" protocol (HTTP REST API) (issue #2066)

CMakeLists.txt

@@ -100,6 +100,7 @@ option(ENABLE_HEADLESS       "Compile the headless binary"              ON)
 option(ENABLE_NLS            "Enable Native Language Support"           ON)
 option(ENABLE_LARGEFILE      "Enable Large File Support"                ON)
 option(ENABLE_ZSTD           "Enable Zstandard compression"             ON)
+option(ENABLE_CJSON          "Enable cJSON support"                     ON)
 option(ENABLE_ALIAS          "Enable Alias plugin"                      ON)
 option(ENABLE_BUFLIST        "Enable Buflist plugin"                    ON)
 option(ENABLE_CHARSET        "Enable Charset plugin"                    ON)
@@ -222,6 +223,12 @@ if(ENABLE_ZSTD)
   add_definitions(-DHAVE_ZSTD)
 endif()
 
+# Check for cJSON
+if(ENABLE_CJSON)
+  pkg_check_modules(LIBCJSON REQUIRED libcjson)
+  add_definitions(-DHAVE_CJSON)
+endif()
+
 # Check for iconv
 find_package(Iconv)
 if(ICONV_FOUND)