Turn DnD on and off for a particular Slack user

[nanorepublica]

Acceptance Criteria

• Given a naptime user is logged in
  When they click a snooze button for a Slack workspace
  Then DnD is activated for that user on the specified workspace.

• Given a naptime user is logged in
  When they click an unsnooze button for a Slack workspace
  Then DnD is deactivated for that user on the specified workspace.