Allow case-insensitive Authorization header lookup

Since reqwest downcases header names:

> Header names are normalized to lower case. In other words, when
> creating a HeaderName with a string, even if upper case characters are
> included, when getting a string representation of the HeaderName, it
> will be all lower case. This allows for faster HeaderMap comparison
> operations.

https://docs.rs/reqwest/latest/reqwest/header/index.html#headername

Author: andrei-21

rust/auth-impls/src/signature.rs

@@ -43,7 +43,16 @@ impl Authorizer for SignatureValidatingAuthorizer {
 		&self, headers_map: &HashMap<String, String>,
 	) -> Result<AuthResponse, VssError> {
 		let auth_header = headers_map
-			.get("Authorization")
+			.iter()
+			.find_map(
+				|(name, value)| {
+					if name.eq_ignore_ascii_case("Authorization") {
+						Some(value)
+					} else {
+						None
+					}
+				},
+			)
 			.ok_or_else(|| VssError::AuthError("Authorization header not found.".to_string()))?;
 
 		if auth_header.len() <= (33 + 64) * 2 {
@@ -125,6 +134,11 @@ mod tests {
 		headers_map.insert("Authorization".to_string(), token);
 		assert_eq!(auth.verify(&headers_map).await.unwrap().user_token, format!("{pubkey:x}"));
 
+		// Test a valid signature with lowercase header key
+		let (token, pubkey) = build_token(now);
+		headers_map.insert("authorization".to_string(), token);
+		assert_eq!(auth.verify(&headers_map).await.unwrap().user_token, format!("{pubkey:x}"));
+
 		// Test a signature too far in the future
 		let (token, _) = build_token(now + 60 * 60 * 24 + 10);
 		headers_map.insert("Authorization".to_string(), token);