Fine-grained Slack notifications

Description

Increase granularity of notifications sent to Slack

Proposal

• Merge request events
• Event will be triggered when a merge request is created/updated/merged

Could become:

• Merge request events
• Merge request created
• Event will be triggered when a merge request is created
• Merge request updated
• Event will be triggered when a merge request is updated
• Merge request merged
• Event will be triggered when a merge request is merged

Rationale

The DEV team is interested only in "Merge request created" events as they are supposed to review the source, put some comments and finally accept or reject it. It would be useful to have a dedicated Slack channel with MRC notification - the DEV team could indicate the MR status using emojis e.g. 🔍 - under investigation, 👍 - accepted, 👎 - rejected.

On the other side, the Product Owner and other teams are only interested in "Merge request accepted". They know which features have been completed and will be available soon. The separate Slack channel would a great place for such notifications.