docs: generation strategies differences between DBAL 3 and 4

Author: lucasmirloup

docs/en/reference/basic-mapping.rst

@@ -389,14 +389,16 @@ Here is the list of possible generation strategies:
 
 -  ``AUTO`` (default): Tells Doctrine to pick the strategy that is
    preferred by the used database platform. The preferred strategies
-   are ``IDENTITY`` for MySQL, SQLite, MsSQL and SQL Anywhere and, for
-   historical reasons, ``SEQUENCE`` for Oracle and PostgreSQL. This
-   strategy provides full portability.
+   are ``IDENTITY`` for MySQL, SQLite, MsSQL, SQL Anywhere and
+   PostgreSQL (on DBAL 4) and, for historical reasons, ``SEQUENCE``
+   for Oracle and PostgreSQL (on DBAL 3). This strategy provides
+   full portability.
 -  ``IDENTITY``: Tells Doctrine to use special identity columns in
    the database that generate a value on insertion of a row. This
    strategy does currently not provide full portability and is
    supported by the following platforms: MySQL/SQLite/SQL Anywhere
-   (``AUTO_INCREMENT``), MSSQL (``IDENTITY``) and PostgreSQL (``SERIAL``).
+   (``AUTO_INCREMENT``), MSSQL (``IDENTITY``) and PostgreSQL (``SERIAL``
+   on DBAL 3, ``GENERATED BY DEFAULT AS IDENTITY`` on DBAL 4).
 -  ``SEQUENCE``: Tells Doctrine to use a database sequence for ID
    generation. This strategy does currently not provide full
    portability. Sequences are supported by Oracle, PostgreSql and