Add quickstart guidance in readme

[jikuja]

Looking good.

There is one addition I would like to see: passing third argument to -RegisterNewNode is now kind of black box:

• When auto-expiration happens?
• What triggers auto-expiration?
• Does it just allow re-register SHIR with same node name when HA is used?

[byran77]

Looking good.

There is one addition I would like to see: passing third argument to -RegisterNewNode is now kind of black box:

• When auto-expiration happens?
• What triggers auto-expiration?
• Does it just allow re-register SHIR with same node name when HA is used?

The third argument to -RegisterNewNode defines the expiration time of offline nodes, that is, if a node has been in offline status for a time exceeding the value, it will be regarded as "expired". All nodes registered to the same IR should hold the same expiration time.

• Auto-expiration happens when 2 conditions are satisfied:
  1. The offline time of the nodes exceeds the duration defined by AE_TIME.
  2. A new node is attempting to register to the IR.
• According to above description, auto-expiration is triggered when a new node is registered to the IR, and the service will then remove the expired offline nodes automatically.
• When HA is used, it supports up to 4 nodes registered to the same IR. Therefore, the IR will still work as long as at least 1 node is alive. If it is disabled, only 1 node is allowed to be registered to IR, and thus re-registry will not work unless the old one is deleted manually.