i15-1: Do not allow resuming the queue when it's empty

[DominicOram]

Following DiamondLightSource/daq-queuing-service#69 resuming an empty queue is nonsensical. The UI should reflect this by not allowing the user to do it, with a tooltip as to why

Acceptance Criteria

• If the queue is empty then you cannot resume it
• There is a tooltip explaining this e.g. "Cannot resume an empty queue, please queue something first"

[zoharma]

I think this means we need to make sure the queue should stop when there are no items left (e.g. change from running to stopped) .

This logic is slightly different from current GDA queue that has the idea of "running" separate to the actual items within. We may want to introduce the idea of "Auto run" as a switch somewhere, so it will start the moment an item is added.

[DominicOram]

I think this means we need to make sure the queue should stop when there are no items left (e.g. change from running to stopped) .

DiamondLightSource/daq-queuing-service#69 makes sure it goes to paused when there is nothing in it. I'm not sure I have strong opinions about adding a stopped state but @jacob720 might.

We may want to introduce the idea of "Auto run" as a switch somewhere, so it will start the moment an item is added.

Yes, I think so. At some point we will need a UI for a number of config options like this, we have a backend config-server for them but not much thought into UI yet

[zoharma]

I think I may have conflated pause and stop actions. I will update the design.