Put puts the given key into the key-value store. A put request increments the revision of the key-value store and generates one event in the event history.
key is the key, in bytes, to put into the key-value store.
value is the value, in bytes, to associate with the key in the key-value store.
lease is the lease ID to associate with the key in the key-value store. A lease value of 0 indicates no lease.
If prev_kv is set, etcd gets the previous key-value pair before changing it. The previous key-value pair will be returned in the put response.