You can offcourse write your own plugin, but if there is an existing solution that would save a lot of time. Searched for GitLab plugins in Slack en via Google, but can’t find anything else then setting up webhooks from GitLab to Slack just for notifications.
I know there is an issue on the issue tracker about creating them from email. Creating them from Slack and Mattermost seems like a great idea.
There is a create issue API, and if you do write a plugin, it could even get contributed into the project saving everybody else lots of time. Might only take you a few hours, are you up for it?
I found the existing issue tracker where “Chat-Ops” (create issue from slack or mattermost) is discussed:
