Function validate_uri 

pub fn validate_uri(
    uri: &str,
    label: &str,
    policy: SsrfPolicy,
) -> Result<Url, AuthError>

Validates that uri has an http(s) scheme and a host.

Sync syntax-level check only. Resolved-IP classification (HTTP-permitted- if-all-internal) is enforced in the async build_ssrf_pinned_client.