Add new slack returner based on incoming webhooks

[cdalvaro]

What does this PR do?

Add a new slack returner based on incoming webhooks

Tests written?

No

Commits signed with GPG?

Yes

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[damon-atkins]

What is the difference between salt/returners/slack_returner and this code?

[cdalvaro]

What is the difference between salt/returners/slack_returner and this code?

slack_retuner does not work with Slack Incoming Webhooks, which is the recommended way to post messages in Slack rather than using the Legacy API Tokens

[damon-atkins]

So can you keep them compatible? What else needs to be changed in salt to work with the new API?

[cdalvaro]

So can you keep them compatible? What else needs to be changed in salt to work with the new API?

Do you mean, what changes are necessary to be made in slack_returner in order to make it compatible with the new API too?

If that is your question, I think that changes should be minimum. Just adding the parameter for the webhook url and based on whether a webhook is passed or an api_token choose the post method.

But this returner is also different in the message format.

[cdalvaro]

Will this PR finally be approved? Or it is needed some change?

[cdalvaro]

Thank you very much, @thatch45 !

[thatch45]

Sure thing, but I likely should not have merged this without tests. If you can get some tests in it would be greatly appreciated!