fix mysql_info crash if PUBLIC role is used on MariaDB 10.11+ (#712)

* tests: grant a privilege to the PUBLIC role to force the module to fail

* skip the PUBLIC role from the users migration example

* Cut the 3rd matching group as it fails to match roles without quotes

The group purpose was to match the closing quotes. We don't need the
value after the TO. So we can ignore this entirely.

* add MariaDB role detection

* Add changelog fragment

* doc: add notes that users_info doesn't support MariaDB roles.

tests/integration/targets/test_mysql_info/tasks/filter_users_info.yml

@@ -31,6 +31,19 @@
             CREATE TABLE IF NOT EXISTS users_info_db.T_UPPER
             (id int, name1 varchar(9), NAME2 varchar(9), Name3 varchar(9))
 
+    # No need for a specific test later. When the module will retrieve the
+    # users privileges, it will fail with an error "1141 - There is no such
+    # grant defined for user 'PUBLIC' on host'%'" if the PUBLIC role is not
+    # handled properly by our module.
+    - name: Mysql_info users_info | Grant to PUBLIC for MariaDB 10.11+
+      community.mysql.mysql_query:
+        query:
+          - >-
+            GRANT SELECT,INSERT,UPDATE,DELETE on users_info_db.* TO PUBLIC
+      when:
+        - db_engine == 'mariadb'
+        - db_version is version('10.11.1', '>=')
+
     # I failed to create a procedure using community.mysql.mysql_query.
     # Maybe it's because we must changed the delimiter.
     - name: Mysql_info users_info | Create procedure SQL file
@@ -277,7 +290,7 @@
         - item.name != 'mysql.sys'
         - item.name != 'mysql.infoschema'
         - item.name != 'mysql.session'
-
+        - item.name != 'PUBLIC'  # MariaDB roles are not supported
 
     # ================================== Cleanup ============================