The lock string to be used when submitting operations on a locked resource.
Before a call to the LockResource method, LockTokens may be set to the tokens returned by a previous lock operation. This is useful when renewing a timeout. The server will respond with a new timeout value, which will be stored in LockTimeout. If the lock request is not a lock refresh, LockTokens must be empty, and will be parsed out of the server response after a successful call to the LockResource method.