## Disappearing member support
Disappearing members are those which may disappear naturally i.e. those running on hosts that may naturally 
power on and off and "disappear" from the network

When disappearing members are used, the following additional signals / actions are provided:
* **"Disappearing MEMBER" remote signals / status**: these must be wired to the actual nodes that may disappear.
* **"Assumed MEMBER" local signals / status**: these aggregate the Power state and binding state of the device

Then the usual remote state/status signals need to be looped-back into their respective "assumed" states.

# Group Node

A group node is designed to aggregate signals and (optionally) actions.

## Actions

Actions such as power and mute are passed down through groups, from parent to child nodes, and eventually to end nodes.

The wiring is a simple one-to-one relationship

| Actions |  Node  | Event
| --------|--------|--------
| Member PC Muting | PC Node | Muting
| Member PC Power  | PC Node | Power
| Member Display Power  | Display Node | Power

An incoming action is passed down to all child nodes.

## Events

Events are collected from child nodes (end or group), aggregated, and then passed up to any parent nodes.

| Events  |  Node  | Event
| --------|--------|--------
| Member PC Muting | PC Node | Muting
| Member PC Power  | PC Node | Power
| Member App Power | App Node | Power

One issue with this is that when the power is turned off, the events from the child devices will stop.

This can be mitigated by using disappearing member, which provides a mechanism for the group node to keep track of the last (assumed) status.

To use this enable `Disappears when power is off` in the members section of the advanced screen for the group node.

When disappearing members are used, the following additional signals / actions are provided:
* **"Disappearing MEMBER" remote signals / status**: these must be wired to the actual nodes that may disappear.
* **"Assumed MEMBER" local signals / status**: these aggregate the Power state and binding state of the device

Then the usual remote state/status signals need to be looped-back into their respective "assumed" states.

Note that this is only required in group nodes when a child node will disappear when the power is off.

The child nodes are wired like this:

| Events                 |  Node     | Event
| -----------------------|-----------|--------
| Member PC Muting       | This Node | MemberPCAssumedMuting
| Member PC Power        | This Node | MemberPCAssumedPower
| Member PC Status       | This Node | MemberPCAssumedStatus
| PC Disappearing Muting | PC        | Muting
| PC Disappearing Power  | PC        | Power
| PC Disappearing Status | PC        | Status

The signal flow looks like this:

```
 ┌─ PC Node ─┐    ┌──────────            This Group Node                ──────────┐   ┌─ parent group or dashboard ─┐
    Status     ->   Disappearing Status -> Member Assumed Status -> Member Status   ->    Event wiring
```

Add some documentation for the group node
Add some documentation for the group node

This add some more details about how the wiring should look for each of the possible configurations.
