Function parse_timestamp 

pub fn parse_timestamp(s: &str) -> Result<Timestamp, String>

Parse an RFC 3339 timestamp string.

Supports formats like:

• “2009-02-13T23:31:30Z”
• “2009-02-13T23:31:30.123456789Z”
• “2009-02-13T23:31:30+01:00”