feat: 💥 API-related Conan, CMake, and preprocessor options redesigned

docs/users_guide/framework_basics/systems_of_quantities.md

@@ -132,10 +132,15 @@ from such an instantiation.
     Quantity specification definitions benefit from an
     [explicit object parameter](https://en.cppreference.com/w/cpp/language/member_functions#Explicit_object_parameter)
     added in C++23 to remove the need for CRTP idiom, which significantly simplifies the code.
-    However, as C++23 is far from being mainstream today, a portability macro `QUANTITY_SPEC()`
+    However, as C++23 is far from being mainstream today,
+    a [portability macro `QUANTITY_SPEC()`](../use_cases/wide_compatibility.md#QUANTITY_SPEC)
     is provided and used consistently through the library to allow the code to compile with C++20
     compilers, thanks to the CRTP usage under the hood.
 
+    See more in the
+    [C++ compiler support](../../getting_started/cpp_compiler_support.md#explicit-this-parameter)
+    chapter.
+
     *[CRTP]: Curiously Recurring Template Parameter
 
 For example, here is how the above quantity kind tree can be modeled in the library: