Need ENUM for fulfillment states

[mherle]

Currently the Fulfillment object has a state property which is of type #/components/schemas/State which just has a code property. Need this to be an ONDC specified ENUM so that we can sync statuses.

Here are the real world statuses that a hyperlocal order goes through:

• Agent is assigned
• Agent is on the way to pickup
• Agent reached pickup
• Agent has picked up the order and is enroute to drop
• Agent has reached the drop location
• Agent has delivered the order
• Order is cancelled (not sure if reasons have to be attributed here such as, Cancelled due to customer denied at door step, Cancelled due to location not found etc)

[BLR-0118]

Added in retail spec 1.0.17 and logistics spec 1.0.14