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##### SUMMARY
<!--- Describe the new feature/improvement briefly below -->
New Percona/MySQL 8 privileges with underscore is not working. 
the following error is coming 

`MSG: invalid privileges string: Invalid privileges specified: frozenset({'BACKUP_ADMIN'})`

##### ISSUE TYPE
- Feature Idea

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->
mysql_user module
most likely the new privileges needs to be added to lib/ansible/modules/database/mysql/mysql_user.py

##### ADDITIONAL INFORMATION
<!--- Describe how the feature would be used, why it is needed and what it would solve -->

<!--- Paste example playbooks or commands between quotes below -->
```yaml

```

<!--- HINT: You can also paste gist.github.com links for larger files -->

supports_check_mode=True,
    )
    login_user = module.params["login_user"]
    login_password = module.params["login_password"]
    user = module.params["user"]
    password = module.params["password"]
    encrypted = module.boolean(module.params["encrypted"])
    host = module.params["host"].lower()
    host_all = module.params["host_all"]
    state = module.params["state"]
    priv = module.params["priv"]
    check_implicit_admin = module.params['check_implicit_admin']
    connect_timeout = module.params['connect_timeout']
    config_file = module.params['config_file']
    append_privs = module.boolean(module.params["append_privs"])
    update_password = module.params['update_password']
    ssl_cert = module.params["client_cert"]
    ssl_key = module.params["client_key"]
    ssl_ca = module.params["ca_cert"]
    db = ''
    sql_log_bin = module.params["sql_log_bin"]
    plugin = module.params["plugin"]
    plugin_hash_string = module.params["plugin_hash_string"]
    plugin_auth_string = module.params["plugin_auth_string"]
    if priv and not (isinstance(priv, str) or isinstance(priv, dict)):
        module.fail_json(msg="priv parameter must be str or dict but %s was passed" % type(priv))
    if priv and isinstance(priv, dict):
        priv = convert_priv_dict_to_str(priv)
    if mysql_driver is None:
        module.fail_json(msg=mysql_driver_fail_msg)