Function parse_username_with_separator_lossy 

pub fn parse_username_with_separator_lossy<P>(
    ext: &Extensions,
    parser: P,
    username_ref: impl AsRef<str>,
    separator: char,
) -> Result<String, Box<dyn Error + Sync + Send>>
where
    P: UsernameLabelParser,
    <P as UsernameLabelParser>::Error: Into<Box<dyn Error + Sync + Send>>,

Like parse_username_with_separator but silently skips UsernameLabelState::Ignored labels instead of erroring.