As an admin, I want to be able to dismiss success/error messages

[camjackson]

Background:

We have a bunch of success and error messages which currently display at the top of the app. At the moment they can't be dismissed in any way. They only go away once another message appears, or if you refresh the page.

User research:

• We should test this with people.

Visual design:

Design questions:

• Should they be individually dismissable?
• Should there be a button to dismiss all messages
• What should the button actually look like?
• Should they automatically fade away after say 5 seconds? (might be a separate card)