need usage hints for add, delete commands

[qrkourier]

Both add --identity and delete --identity options exist, but they are inconsistent, and there's no hint to explain the difference.

The add --identity option requires a string like myIdentityName that determines the basename of the JSON identity config file created after enrollment.

The delete --identity option requires the identity's "Identifier" property, which appears to be a string that represents the filesystem path to the JSON identity config file, but may be a string representing the relative or absolute path, depending upon the options passed when the tunnel process was invoked.