Restricted comments for Approvers

Problem

Currently, it's not possible to leave restricted comments for Approvers who do not have application access to Jira.

Suggestion

Allow comment visibility configuration for Portal

Why is it important

• Example use case

  When we send an issue to an Approver, often we need to write a private
  comment for her - for example, to give her additional information that
  might help her to make a decision about approving or rejecting the request.
  Sometimes this information may include technical details or sensitive data
  that cannot be shared to other person. Thus, this kind of comment should
  be visible to the Approver only, and not to the Request participants.
  Moreover, usually the Approver does not have a JIRA account so we cannot
  use the internal comments for that.