I cannot find any reference, description, or meaning of the usage of the **0\*** multiplicity operator in the document or in [RFC7565](https://www.rfc-editor.org/rfc/rfc7565.html) or [RFC 5234](https://www.rfc-editor.org/rfc/rfc5234.html). ``` userpart = unreserved / sub-delims 0*( unreserved / pct-encoded / sub-delims ) ```
