Backend: Provide endpoints for retrieving device nodes and Minion nodes

The backend and BFF service need to provide a way to query for nodes.

• The frontend should be able to get Minion nodes and device nodes in separate queries
• The response should include the node's status, and associated time series info
• The BFF is a good place to abstract away things like: Minion status is red/green depending on how old the last heartbeat is, rather than tracking that as the state of the node itself