User can now use a JsonString as a key or a value

test/JsonObject/subscript.cpp

@@ -141,6 +141,18 @@ TEST_CASE("JsonObject::operator[]") {
     REQUIRE(expectedSize <= doc.memoryUsage());
   }
 
+  SECTION("should duplicate a non-static JsonString key") {
+    obj[JsonString("hello", false)] = "world";
+    const size_t expectedSize = JSON_OBJECT_SIZE(1) + JSON_STRING_SIZE(6);
+    REQUIRE(expectedSize == doc.memoryUsage());
+  }
+
+  SECTION("should not duplicate a static JsonString key") {
+    obj[JsonString("hello", true)] = "world";
+    const size_t expectedSize = JSON_OBJECT_SIZE(1);
+    REQUIRE(expectedSize == doc.memoryUsage());
+  }
+
   SECTION("should ignore null key") {
     // object must have a value to make a call to strcmp()
     obj["dummy"] = 42;

test/JsonVariant/set.cpp

@@ -71,6 +71,26 @@ TEST_CASE("JsonVariant and strings") {
 
     REQUIRE(variant == "hello");
   }
+
+  SECTION("stores static JsonString by reference") {
+    char str[16];
+
+    strcpy(str, "hello");
+    variant.set(JsonString(str, true));
+    strcpy(str, "world");
+
+    REQUIRE(variant == "hello");
+  }
+
+  SECTION("stores non-static JsonString by copy") {
+    char str[16];
+
+    strcpy(str, "hello");
+    variant.set(JsonString(str, false));
+    strcpy(str, "world");
+
+    REQUIRE(variant == "hello");
+  }
 }
 
 TEST_CASE("JsonVariant with not enough memory") {