Allow uppercase in variable names for Galera wsrep variables (#501)

* Allow uppercase in variable names for Galera wsrep variables

* Changelog fragment for regex change

* Corrected for excessive line lengths

* Update changelogs/fragments/mysql_variables_allow_uppercase_identifiers.yml

---------

Co-authored-by: Andrew Klychkov <aaklychkov@mail.ru>

changelogs/fragments/mysql_variables_allow_uppercase_identifiers.yml

@@ -0,0 +1,6 @@
+---
+bugfixes:
+  - mysql_variables - add uppercase character pattern to regex to allow GLOBAL
+    variables containing uppercase characters.
+    This recognizes variable names used in Galera, for example, ``wsrep_OSU_method``,
+    which breaks the normal pattern of all lowercase characters (https://github.com/ansible-collections/community.mysql/pull/501).

plugins/modules/mysql_variables.py

@@ -199,7 +199,7 @@ def main():
 
     if mysqlvar is None:
         module.fail_json(msg="Cannot run without variable to operate with")
-    if match('^[0-9a-z_.]+$', mysqlvar) is None:
+    if match('^[0-9A-Za-z_.]+$', mysqlvar) is None:
         module.fail_json(msg="invalid variable name \"%s\"" % mysqlvar)
     if mysql_driver is None:
         module.fail_json(msg=mysql_driver_fail_msg)