Accept serial number as optional arg for connecting via panorama

[amylieb]

Environment

• napalm-panos version: 0.6.2

Proposed Functionality

Allow for 'serial' value in optional_args in the initializer for this class that can be then referenced in the open method so that an xapi connection can be made to a device via panorama.

Use Case

Connecting to devices through panorama instead of directly - our firewall team gave me an API key that works against panorama, they don't want to manage credentials on firewalls individually. The code changes are pretty simple since pan.xapi will take "serial" in as an argument and then add &target=<serial> to its URL queries.

[amylieb]

I've actually implemented this in my own environment so that I can leverage this library without maintaining a fork- here's the relevant code:

class PANOS(PANOSDriver):
    """
    PANOS Parser
    """

    def __init__(self, hostname, username, password, timeout=60, optional_args=None):

        super().__init__(hostname, username, password, timeout, optional_args)

        self.serial = None
        if optional_args:
            self.serial = optional_args.get("serial")
            

    def open(self):
        """PANOS version of `open` method, see NAPALM for documentation."""
        try:
            if self.api_key:
                self.device = pan.xapi.PanXapi(hostname=self.hostname, api_key=self.api_key, serial=self.serial)
            else:
                self.device = pan.xapi.PanXapi(
                    hostname=self.hostname,
                    api_username=self.username,
                    api_password=self.password,
                    serial=self.serial
                )
        except ConnectionException as exc:
            raise ConnectionException(str(exc))
        if not self.locked and self.session_config_lock:
            self._lock()