Get response on Assist Satellite device

[balloob]

This extracts #1143 (comment) into it's own proposal. It is meant to work with the built-in Home Assistant conversation agent.

Context

With the introduction of Assist Satellite entities, we now have a representation of devices that allow users to talk with Assist. Some of these devices are also able to start a conversation with a user without the user initiating the conversation via a wake-word or button press.

The Home Assistant built-in conversation agent works with sentence matching. This makes it hard to extend it and continue a conversation.

Proposal

Introduce a new Assist Satellite service get_response to allow Home Assistant to announce a message on an Assist Satellite device and listen to a response from the user. The response is sent through STT and the raw text is returned as the service response value.

(In the future, we could extend intent system to parse the responses, but step 1 is just to get the raw text back)

Use cases:

• Ask user what music they want to listen to, sent the response to search of a media player

Solution

Add a new service assist_satellite.get_response that allows targeting assist_satellite entities that support a new supported feature GET_RESPONSE.

The service will have the following service fields:

• start_message and start_media_id. These fields will work exactly like the announce service: either one has to be provided. If no media ID is provided, use TTS of the selected pipeline to generate media.