Change string copy policy: only string literal are stored by pointer

extras/tests/JsonDocument/add.cpp

@@ -26,7 +26,7 @@ TEST_CASE("JsonDocument::add(T)") {
                          });
   }
 
-  SECTION("const char*") {
+  SECTION("string literal") {
     doc.add("hello");
 
     REQUIRE(doc.as<std::string>() == "[\"hello\"]");
@@ -35,6 +35,17 @@ TEST_CASE("JsonDocument::add(T)") {
                          });
   }
 
+  SECTION("const char*") {
+    const char* value = "hello";
+    doc.add(value);
+
+    REQUIRE(doc.as<std::string>() == "[\"hello\"]");
+    REQUIRE(spy.log() == AllocatorLog{
+                             Allocate(sizeofPool()),
+                             Allocate(sizeofString("hello")),
+                         });
+  }
+
   SECTION("std::string") {
     doc.add("example"_s);
     doc.add("example"_s);