[MM-356] Add feature to subscribe to release and workflow events

[ayusht2810]

Summary

• Added feature to publish workflow failure events

Screenshot

Ticket Link

Fixes #722 Fixes #565

What to test?

• Update the webhook for the repo to receive notifications for workflow events
• Create a subscription for a repo with a subscription enabled for workflow events
• Create workflow in which a particular jobs fail
• Check for the event received in the subscribed channel

Checklist

• [x] Completed dev testing
• [x] make test Ran test cases and ensured they are passing
• [x] make check-style Ran style check and ensured both webapp and server pass the checks

[Kshitij-Katiyar]

@mickmister Fixed the comments, Please have a look.

[wiggin77]

This PR is going to have a significant merge conflict with https://github.com/mattermost/mattermost-plugin-github/pull/808/files

Does anyone have an opinion on which is more important?: release and workflow subscriptions vs discussions and comment

[raghavaggarwal2308]

@wiggin77 In both the PRs we mainly adding new functions not updating the existing functions much. I think it won't be difficult to fix the conflicts in this case. So, we can merge whichever PR is ready first. Please let me know your opinions on this.

[wiggin77]

@wiggin77 In both the PRs we mainly adding new functions not updating the existing functions much. I think it won't be difficult to fix the conflicts in this case. So, we can merge whichever PR is ready first. Please let me know your opinions on this.

Ok, let's get this one merged first.

[mattermost-build]

This PR has been automatically labelled "stale" because it hasn't had recent activity. A core team member will check in on the status of the PR to help with questions. Thank you for your contribution!

[mattermost-build]

This PR has been automatically labelled "stale" because it hasn't had recent activity. A core team member will check in on the status of the PR to help with questions. Thank you for your contribution!