Skeleton of Discovery Implementation

[krkeegan]

Proposed change

This is a functioning basic implementation of the Discovery feature. It lacks lots of documentation, and is only implemented on Dimmers. The idea is this:

1. There are some global yaml settings for discovery such as discovery_topic_base and discovery_ha_status
2. There is a global setting for device_info_template that allows the user to define a device template that can be reused as a variable in the discovery templates. @schirner had implemented something like this, and I agree this is very handy. This is likely to be reused in every template.
3. By default each device class will look in it's subkey under the mqtt key in the config.yaml file for the discovery templates. So dimmers look to mqtt->dimmer by default.
4. Inside this class, a discovery_entities key is defined. This key must have a component subkey and config key. The config key must include at minimum a unique_id. Other HomeAssistant config settings also need to be defined.
5. The templates have a lot of variables available to them including: name, address, name_user_case, engine, model, firmware, modem_addr, device_info_template. Additionally all topics defined in yaml are also available.
6. The discovery topics are automatically generated, I don't see any reason why a user would need to edit these, they do not have any effect on how HomeAssistant functions.

Customization

As referenced in the min_hops addition, users can create new discovery classes that can be used on one or more devices. By specifying discovery_class as an config_extra key for the device. The value is a reference to a key under the mqtt section. This new subkey would then need to contain a discovery_entities key as defined above.

Additional information

• This PR is related to issue: MQTT discovery automatic configuration #128

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• Tests have been added to verify that the new code works.
• Code documentation was added where necessary
• Documentation added/updated

Below is a sample of the published topic homeassistant/light/4f.23.38/4f.23.38_light/config using the config settings shown in the attached commits:

{
  "uniq_id": "4f.23.38_light",
  "name": "dimmer",
  "cmd_t": "insteon/4f.23.38/level",
  "stat_t": "insteon/4f.23.38/state",
  "brightness": true,
  "schema": "json",
  "device": {
  "ids": "4f.23.38",
  "mf": "Insteon",
  "mdl": "DIMMABLE_LIGHTING (0x01): '2477D' (0x20) 'SwitchLinc Dimmer (Dual-Band)'",
  "sw": "69",
  "name": "dimmer",
  "via_device": "41.ee.e6"
}
}

[krkeegan]

Oh, I should note, the current design publishes all discovery entities when IM starts up and republishes them anytime it see HA restart. It seems to be working fine.