docs: documentation updated for C++ modules

docs/getting_started/installation_and_usage.md

@@ -12,11 +12,34 @@
     a [preprocessor macro](../users_guide/framework_basics/systems_of_quantities.md#defining-quantities)
     providing a backward-compatible way to use it.
 
-    As of today, the library compiles fine on the following compilers (or newer):
+    The below table provides the minimum compiler version required to compile the code using the
+    specific feature:
 
-    - gcc-12
+    | Feature              | gcc  | clang | apple-clang | MSVC |
-    - clang-16
+    |----------------------|:----:|:-----:|:-----------:|:----:|
-    - apple-clang-15
+    | **Minimum support**  |  12  |  16   |     15      | None |
+    | **`std::format`**    | None | None  |    None     | None |
+    | **C++ modules**      | None |  17   |    None     | None |
+    | **C++23 extensions** | None | None  |    None     | None |
+
+    More requirements for C++ modules support can be found in the
+    [CMake's documentation](https://cmake.org/cmake/help/latest/manual/cmake-cxxmodules.7.html).
+
+
+## Modules
+
+The **mp-units** library provides the following C++ modules.
+
+```mermaid
+flowchart TD
+    mp_units --- mp_units.systems --- mp_units.core
+```
+
+| C++ Module         | CMake Target         | Contents                                |
+|--------------------|----------------------|-----------------------------------------|
+| `mp_units.core`    | `mp-units::core`     | Core library framework                  |
+| `mp_units.systems` | `mp-units::systems`  | All the systems of quantities and units |
+| `mp_units`         | `mp-units::mp-units` | Core + Systems                          |
 
 
 ## Repository Structure and Dependencies
@@ -60,10 +83,12 @@ This repository contains three independent CMake-based projects:
 
     This is why our projects have two entry points:
 
-    - _./CMakeLists.txt_ is to be used by projects developers to build **ALL** the project code with really
+    - _./CMakeLists.txt_ is **to be used by projects developers** to build **ALL** the project code
-    restrictive compilation flags,
+      with really restrictive compilation flags,
-    - _./src/CMakeLists.txt_ contains only a pure library definition and should be used by the customers
+    - _./src/CMakeLists.txt_ contains only a pure library definition and **should be used by the
-    that prefer to use CMake's `add_subdirectory()` to handle the dependencies.
+      customers** that prefer to use CMake's
+      [`add_subdirectory()`](https://cmake.org/cmake/help/latest/command/add_subdirectory.html) to
+      handle the dependencies.
 
     To learn more about the rationale, please check our
     [FAQ](faq.md#why-dont-we-have-cmake-options-to-disable-building-of-tests-and-examples).
@@ -138,6 +163,16 @@ tools.build:compiler_executables={"c": "gcc-12", "cpp": "g++-12"}
 
 ## Build Options
 
+### Conan Options
+
+[cxx_modules](#cxx_modules){ #cxx_modules }
+
+:   [:octicons-tag-24: 2.2.0][cxx modules support] · :octicons-milestone-24: `True`/`False` (Default: `False`)
+
+    Configures CMake to add C++ modules to the list of default targets.
+
+[cxx modules support]: https://github.com/mpusz/mp-units/releases/tag/v2.2.0
+
 ### Conan Configuration Properties
 
 [`user.build:all`](#user-build-all){ #user-build-all }
@@ -146,7 +181,8 @@ tools.build:compiler_executables={"c": "gcc-12", "cpp": "g++-12"}
 
     Enables compilation of all the source code, including tests and examples. To support this, it requires some additional Conan build dependencies described in
     [Repository Structure and Dependencies](#repository-structure-and-dependencies).
-    It also runs unit tests during Conan build (unless `tools.build:skip_test`
+    It also runs unit tests during Conan build (unless
+    [`tools.build:skip_test`](https://docs.conan.io/2/reference/commands/config.html?highlight=tools.build:skip_test#conan-config-list)
     configuration property is set to `True`).
 
 [build all support]: https://github.com/mpusz/mp-units/releases/tag/v0.8.0
@@ -166,6 +202,15 @@ tools.build:compiler_executables={"c": "gcc-12", "cpp": "g++-12"}
 
 ### CMake Options
 
+[`MP_UNITS_BUILD_CXX_MODULES`](#MP_UNITS_BUILD_CXX_MODULES){ #MP_UNITS_BUILD_CXX_MODULES }
+
+:   [:octicons-tag-24: 2.2.0][build_cxx_modules support] · :octicons-milestone-24: `ON`/`OFF` (Default: `OFF`)
+
+    Adds C++ modules to the list of default targets.
+
+    [build_cxx_modules support]: https://github.com/mpusz/mp-units/releases/tag/v2.2.0
+
+
 [`MP_UNITS_AS_SYSTEM_HEADERS`](#MP_UNITS_AS_SYSTEM_HEADERS){ #MP_UNITS_AS_SYSTEM_HEADERS }
 
 :   [:octicons-tag-24: 2.0.0][as system headers support] · :octicons-milestone-24: `ON`/`OFF` (Default: `OFF`)
@@ -175,15 +220,6 @@ tools.build:compiler_executables={"c": "gcc-12", "cpp": "g++-12"}
     [as system headers support]: https://github.com/mpusz/mp-units/releases/tag/v2.0.0
 
 
-[`MP_UNITS_BUILD_CXX_MODULES`](#MP_UNITS_BUILD_CXX_MODULES){ #MP_UNITS_BUILD_CXX_MODULES }
-
-:   [:octicons-tag-24: 2.2.0][build_cxx_modules support] · :octicons-milestone-24: `ON`/`OFF` (Default: `OFF`)
-
-    Add C++ modules to the list of default targets.
-
-    [build_cxx_modules support]: https://github.com/mpusz/mp-units/releases/tag/v2.2.0
-
-
 [`MP_UNITS_BUILD_LA`](#MP_UNITS_BUILD_LA){ #MP_UNITS_BUILD_LA }
 
 :   [:octicons-tag-24: 2.0.0][build la support] · :octicons-milestone-24: `ON`/`OFF` (Default: `ON`)
@@ -208,7 +244,7 @@ tools.build:compiler_executables={"c": "gcc-12", "cpp": "g++-12"}
 :   [:octicons-tag-24: 2.0.0][use libfmt support] · :octicons-milestone-24: `ON`/`OFF` (Default: `ON`)
 
     Forces usage of [{fmt}](https://github.com/fmtlib/fmt) library instead of the C++20 Standard
-    Library feature.
+    Library features.
 
     [use libfmt support]: https://github.com/mpusz/mp-units/releases/tag/v2.0.0
 
@@ -293,6 +329,9 @@ The following steps may be performed to obtain an official library release:
     [requires]
     mp-units/2.1.0
 
+    [options]
+    mp-units:cxx_modules=True
+
     [layout]
     cmake_layout
 
@@ -350,6 +389,9 @@ with the following differences:
     [requires]
     mp-units/2.2.0@mpusz/testing
 
+    [options]
+    mp-units:cxx_modules=True
+
     [layout]
     cmake_layout
 
@@ -396,7 +438,7 @@ you should:
 
 ```shell
 git clone https://github.com/mpusz/mp-units.git && cd units
-conan build . -pr <your_conan_profile> -s compiler.cppstd=20 -c user.build:all=True -b missing
+conan build . -pr <your_conan_profile> -s compiler.cppstd=23 -o cxx_modules=True -c user.build:all=True -b missing
 ```
 
 The above will download and install all of the dependencies needed for the development of the library,
@@ -442,7 +484,7 @@ After that, you can either:
 To test CMake installation and Conan packaging or create a Conan package run:
 
 ```shell
-conan create . --user <username> --channel <channel> -pr <your_conan_profile> -s compiler.cppstd=20 -c user.build:all=True -b missing
+conan create . --user <username> --channel <channel> -pr <your_conan_profile> -s compiler.cppstd=20 -o cxx_modules=True -c user.build:all=True -b missing
 ```
 
 The above will create a Conan package and run tests provided in _./test_package_ directory.

docs/index.md

@@ -25,11 +25,19 @@ The library source code is hosted on [GitHub](https://github.com/mpusz/mp-units)
     a [preprocessor macro](users_guide/framework_basics/systems_of_quantities.md#defining-quantities)
     providing a backward-compatible way to use it.
 
-    As of today, the library compiles fine on the following compilers (or newer):
+    The below table provides the minimum compiler version required to compile the code using the
+    specific feature:
+
+    | Feature              | gcc  | clang | apple-clang | MSVC |
+    |----------------------|:----:|:-----:|:-----------:|:----:|
+    | **Minimum support**  |  12  |  16   |     15      | None |
+    | **`std::format`**    | None | None  |    None     | None |
+    | **C++ modules**      | None |  17   |    None     | None |
+    | **C++23 extensions** | None | None  |    None     | None |
+
+    More requirements for C++ modules support can be found in the
+    [CMake's documentation](https://cmake.org/cmake/help/latest/manual/cmake-cxxmodules.7.html).
 
-    - gcc-12
-    - clang-16
-    - apple-clang-15
 
 ```cpp
 #include <mp-units/ostream.h>