Improved XML serialization

- Use quick_xml and serde for all XML response returned by the S3 API.
- Include tests for all structs used to generate XML
- Remove old manual XML escaping function which was unsafe

src/api/encoding.rs

@@ -1,13 +1,5 @@
 //! Module containing various helpers for encoding
 
-/// Escape &str for xml inclusion
-pub fn xml_escape(s: &str) -> String {
-	s.replace("&", "&")
-		.replace("<", "&lt;")
-		.replace(">", "&gt;")
-		.replace("\"", "&quot;")
-}
-
 /// Encode &str for use in a URI
 pub fn uri_encode(string: &str, encode_slash: bool) -> String {
 	let mut result = String::with_capacity(string.len() * 2);
@@ -28,12 +20,3 @@ pub fn uri_encode(string: &str, encode_slash: bool) -> String {
 	}
 	result
 }
-
-/// Encode &str either as an uri, or a valid string for xml inclusion
-pub fn xml_encode_key(k: &str, urlencode: bool) -> String {
-	if urlencode {
-		uri_encode(k, true)
-	} else {
-		xml_escape(k)
-	}
-}