[Notifier] Add better example for Slack DSN

[Nyholm]

Slacks API documentation is a mess!

This small change would make it more clear that one should use their webhook URL's parameters.

[javiereguiluz]

This might be better than the current situation ... but to me it's the same. How can anybody understand what XXXX means? Maybe we need to add a super short comment before each SLACK_DSN example explaining what's the ID and those XXXXX. Thanks!

[Nyholm]

Maybe this comment is helpful (PR updated)

[javiereguiluz]

I was thinking about something like this:

# .env
# when using the Slack channel ID
SLACK_DSN=slack://default/ID
# when using Slack webhooks (https://hooks.slack.com/services/T.../B.../X...)
SLACK_DSN=slack://default/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX

I don't know if the ID is the channel ID; it's only an example. Also, I think we should use the same pattern as the Slack API docs for the different webhook parts. See https://api.slack.com/messaging/webhooks

[Nyholm]

I think slack://default/ID belongs to a deprecated API that we've removed support for. But Im not sure.

If Im correct, then slack://default/ID cannot be used..

[OskarStark]

It took me hours to get it running using an incoming Webhoook like this:

https://github.com/sonata-project/dev-kit/blob/master/.env.dist

[wouterj]

The ID here refers to the T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX bit, which is the confusing part here.

(and btw, I agree that the Notifier docs are quite a mess. The component evolved a lot after its initial launch, the original document structure no longer fits the broad set of chatters and their different features)

[javiereguiluz]

Tobias thanks for improving this. Hopefully it will avoid the confusion that many have faced so far with these docs.