Migrate CONF_WEBHOOK_ID to homeassistant.const

[rohankapoorcom]

Description:

CONF_WEBHOOK_ID = 'webhook_id' is currently defined in the webhook automation as well as the ifttt component. As part of #15376, I was going to add it to the mailgun component as well (and it will likely be needed in other components as well as they migrate to use the new webhooks). I think it makes more sense to be be a part of the homeassistant.const package since it is shared.

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass

[fabaff]

Looks good to me 🐦

[rohankapoorcom]

@fabaff - I noticed a couple of instances in ifttt where webhook_id is used directly as a string still (example). Okay to swap it over to the constant in this pull request or would a new one be preferred for that?

[fabaff]

You can do it in this PR, would be faster than waiting for two round of CI to pass.

[rohankapoorcom]

Great, should be ready to go then!

[awarecan]

This better keep it as string literal, since it is not part of configuration.

[awarecan]

I don't think we should change the webhook_id used out of context of configuration to CONF_WEBHOOK_ID e.g., those usage in your last two commits

[rohankapoorcom]

I don't think we should change the webhook_id used out of context of configuration to CONF_WEBHOOK_ID e.g., those usage in your last two commits

That was one of the things I was also concerned about. Is it acceptable to create a new constant under the ID section and then use that for CONF_WEBHOOK_ID as well as the places that are not actually configuration?

Something like this:

WEBHOOK_ID = 'webhook_id`'
CONF_WEBHOOK_ID = WEBHOOK_ID

[balloob]

No. Just leave the automation as-is. Let's not start aliasing constants.