Add support for home assistant's STATE_OFF

[SteveMicroNova]

What does this change intend to accomplish?

Support STATE_OFF for use with home assistant media_player entities

Checklist

• Have you tested your changes and ensured they work?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• If applicable, have you updated the documentation/manual?
• If applicable, have you updated the CHANGELOG?
• Does your submission pass linting & tests? You can test on localhost using ./scripts/test
• Have you written new tests for your core features/changes, as applicable?

[SteveMicroNova]

I forget if this needed new tests to be made for it since we only talked about this verbally a few days ago and I have since fed my brain into a taffy puller with the various things I've been touching lately

Let me know what changes this needs, if any, and I'll make a rapid release so it can be used with the upcoming hacs_amplipi update

[linknum23]

Suggested change

	""" Indicate that a zone is set to STATE_OFF within home assistant """
	""" Indicate that a zone is set to STATE_OFF used for tracking a power off state for external interfaces that treat a zone as a media player with an on/off button. Used for integrations such as home assistant. Use the following mapping to use as an on/off indicator:
	- ON: source_id != ZONE_OFF
	- OFF: source_id == ZONE_OFF
	To turn off: set to ZONE_OFF.
	To turn back on: set to SOURCE_DISCONNECTED (to wait for the user to change an input) or set to any valid source id to start playing something.
	"""

[linknum23]

That probably needs a touch of rework but gets the general concept past.

[SteveMicroNova]

I've added a less verbose version in my recent commit, see here:

"""
Indicate that a zone is considered off for the purpose of external interfaces such as home assistant

ON = source_id != ZONE_OFF
OFF = source_id == ZONE_OFF

To turn off: set to ZONE_OFF
To turn on: set to SOURCE_DISCONNECTED or any valid source_id
"""

[linknum23]

As discussed this looks good!