Add support for Google chat (webhook only)

[elervik]

Hi, couldnt find any contribution instructions for your project and this is my first contrib back upstream.

Our team is currently stuck using Google services, especially Google Chat. I didnt want to have a slack only as a proxy and therefore I have extended your code to support posting messages to Google Chat Spaces via webhook using a simple wrapper (https://pkg.go.dev/go.seankhliao.com/gchat) package.

I couldnt test the reactions in the slack thread, but google chat webhook, slack webhook and slack client seems to work:

[CLAassistant]

All committers have signed the CLA.

[dghubble]

This seems like a very niche feature. I eventually managed to find this within Google's many chat-like things, but webhooks are not available to regular Google Accounts. I imagine you have some different setup?

Docs: https://developers.google.com/workspace/chat/quickstart/webhooks

[elervik]

This seems like a very niche feature. I eventually managed to find this within Google's many chat-like things, but webhooks are not available to regular Google Accounts. I imagine you have some different setup?

Docs: https://developers.google.com/workspace/chat/quickstart/webhooks

True, the webhook can only post to google chat spaces. "Google Workspace" is often used by mid/large organizations, and Google Chat (and "chat spaces") are similar (but worse) to Slack, Discord etc. We are stuck with it for atleast a couple of years so I dont mind maintaining a fork if that is a better solution for you =)

[dghubble]

I see, Google Workspace is what used to be called Google GSuite and I think Google Chat Spaces is part of that. I'm not neccessarily opposed, I just don't have an easy way to validate or support this I think?

[elervik]

I didn't event consider that you would need access to a google workspace to verify and or maintain this feature when I wrote it. The only free alternative seems to be a Trial subscription (limited in time) or be invited as a guest to someones existing workspace, and they would have to create the chat space and generate webhook URL to it.. Let's close this PR and Ill just keep the fork up to date until a solution presents itself. :) Thank you for your time

[dghubble]

Sounds good, thanks for using and contributing.