2.0 Errors for removing a subnet

[Carla Berkers]

As discussed with Andres, Blake and Rich via email.
There are three types of errors we should display when removing a subnet:

1. MAAS provides DHCP to nodes or devices on the subnet
This subnet cannot be removed as there are nodes that have an IP address obtained through DHCP services on this subnet. Release these nodes in order to proceed.

2. MAAS provides DHCP to the subnet but has no IP addresses allocated at the moment of removal.
Are you sure you want to remove this subnet? ["Cancel" textlink] ["Remove" orange CTA]

3. MAAS does not provide DHCP to nodes on the subnet
Are you sure you want to remove this subnet? Beware IP addresses on devices on this subnet might not be retained. ["Cancel" textlink] ["Remove" orange CTA]