Add URL targeting and Notification style messaging to admin message functionality (for in app feedback)

Problem

Currently, GitLab has no good way to collect directed feedback from users. The general feedback button inside the application only allows users to submit issues to a general issue board. This does not allow Product, Product Marketing, or UX to collect feedback on specific items that require timely user feedback. As a result, we have to rely on intuition rather than data in many cases.

Solution

As a v1, we should alter the Broadcast message functionality in the following way:

• Add the ability to target a broadcast message by URL
• Add the ability to chose a Broadcast message "Type" that allows the user to choose between the current banner message, and a new unobtrusive notification style message.
• Notification messages should allow for line breaks
  anchor tags (with style attributes)

Prototype

For reference here is what the feature looks like today: