Add system note on change incidents severity

Merged Vitali Tatarintev requested to merge ck3g-add-system-note-on-change-severity into master

What does this MR do?

Adds a system note every time an incident's severity updated.

Info: The functionality is hidden behind a add_severity_system_note feature flag. Run Feature.enable(:add_severity_system_note, true) from Rails console to enable it on your localhost.

Feature flag rollout issue: #251110 (closed)

Screenshots

Screenshot_2020-09-17_at_10.09.44

Demo

Don't mind the old icon in the demo.

Severity_SystemNote_Demo

Does this MR meet the acceptance criteria?

Conformity

Availability and Testing

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

  • ~~Label as security and @ mention @gitlab-com/gl-security/appsec~~
  • The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
  • Security reports checked/validated by a reviewer from the AppSec team
Edited by Vitali Tatarintev