Introduce the concept of a domain lifecycle state.

[poetinger]

This PR will:

• Introduce the concept of a lifecycle state for domains
• Introduce the ability for a user to transition the lifecycle state
• Introduce the ability for a user to query the current lifecycle state

Limitations:

• The only two lifecycle states that will exist, for now, are initialisation and operational
• The only supported transition is initialisation->operational
• For now, there is no meaning to the two lifecycle states, but this can/will change in the future
• For now, the transition and state can only be applied to all domains

[poetinger]

Converted to draft, still needs tests.