Post: Language codes are now normalized (#244)

* Post: Language codes are now normalized

Ref readthedocs/readthedocs.org#10750

* Mention redirects

Author: stsewd

language-codes-are-now-normalized.rst

@@ -0,0 +1,36 @@
+.. post:: October 24, 2023
+   :tags: docs, languages, translations
+   :category: Changelog
+   :author: Santos
+   :location: CUE
+
+Language codes are now normalized
+=================================
+
+The following language codes are now normalized to be lowercase and use a dash as a separator instead of an underscore:
+
+- ``nb_NO`` is now ``nb-no``
+- ``pt_BR`` is now ``pt-br``
+- ``es_MX`` is now ``es-mx``
+- ``uk_UA`` is now ``uk-ua``
+- ``zh_CN`` is now ``zh-cn``
+- ``zh_TW`` is now ``zh-tw``
+
+This change affects the following areas:
+
+API:
+   - When creating or updating projects, you must now use the new normalized language codes.
+   - The API responses will include the new normalized language codes.
+
+Docs and download URLs:
+   Previous URLs from projects using the old language codes will redirect to the new normalized language codes.
+   For example:
+
+   - ``https://docs.readthedocs/pt_BR/latest/`` will redirect to ``https://docs.readthedocs/pt-br/latest/``.
+   - ``https://docs.readthedocs/_/downloads/pt_BR/latest/pdf/`` will redirect to ``https://docs.readthedocs/_/downloads/pt-br/latest/pdf/``.
+
+Redirects:
+  If you had redirects using the old language codes in the ``From URL`` field,
+  they were automatically updated to use the new normalized language codes.
+
+This change was implemented to ensure more `readable and clean URLs <https://en.wikipedia.org/wiki/Clean_URL>`__.