Document required_conan_version for recipes (#1788)

* add docs

* add ref

reference/conanfile/other.rst

@@ -88,4 +88,28 @@ Optional parameters:
   DYLIB_LIBRARY_PATH are defined in the command execution adding the values of the "lib" and "bin" folders of the dependencies.
   Allows executables to be easily run using shared libraries from its dependencies.
 - **with_login** (Optional, Defaulted to ``True``): Pass the ``--login`` flag to :command:`bash` command when using ``win_bash`` parameter.
-  This might come handy when you don't want to create a fresh user session for running the command.
+  This might come handy when you don't want to create a fresh user session for running the command.
+
+.. _conanfile_required_version:
+
+Requiring a Conan version for the recipe
+----------------------------------------
+
+A required Conan version can be declared in the `conanfile.py` using ``required_conan_version`` to
+throw an error when the Conan version installed does not meet the criteria established by the
+variable. To add ``required_conan_version`` to a `conanfile.py` just declare it before the recipe
+class definition:
+
+  ..  code-block:: python
+      :emphasize-lines: 3
+      
+      from conans import ConanFile
+
+      required_conan_version = ">=1.27.1"
+
+      class Pkg(ConanFile):
+          settings = "os", "compiler", "arch", "build_type"
+          ...
+
+It is also possible to declare ``required_conan_version`` at configuration level for the whole client
+adding it to the :ref:`conan.conf<conan_conf>` file.

reference/config_files/conan.conf.rst

@@ -224,7 +224,8 @@ configured. It only accepts the follow time intervals: minutes, hours and days.
 
 The ``required_conan_version`` variable validates if the current Conan client version is valid according to its version. When it's not
 according to the required version or its range, Conan raises an exception before running any command. It accepts SemVer format, including version range.
-This configuration is useful When a company wants to align the Conan client version used by all teams.
+This configuration is useful when a company wants to align the Conan client version used by all teams. This can be also specified at
+:ref:`recipe level<conanfile_required_version>` if you need adding this information just for certain recipes.
 
 Storage
 +++++++