Revert "Allow a Message to be decomposed into a MessageBuilder (#633)" (#649)

This reverts commit aadcc0f83c.

Co-authored-by: Alexis Mousset <contact@amousset.me>

src/message/mod.rs

@@ -480,22 +480,6 @@ impl Message {
         MessageBuilder::new()
     }
 
-    /// Turn a finalized message back into a builder and body.
-    pub fn into_parts(self) -> (MessageBuilder, Body) {
-        let maybe_encoding = self.headers.get::<ContentTransferEncoding>();
-        let builder = MessageBuilder {
-            envelope: Some(self.envelope),
-            headers: self.headers,
-        };
-        let mut out = Vec::new();
-        match self.body {
-            MessageBody::Mime(p) => p.format(&mut out),
-            MessageBody::Raw(r) => out.extend_from_slice(&r),
-        }
-        let body = out.into_body(maybe_encoding);
-        (builder, body)
-    }
-
     /// Get the headers from the Message
     pub fn headers(&self) -> &Headers {
         &self.headers
@@ -666,32 +650,4 @@ mod test {
             assert_eq!(36, id.len());
         }
     }
-
-    #[test]
-    fn test_into_parts() {
-        // Tue, 15 Nov 1994 08:12:31 GMT
-        let date = SystemTime::UNIX_EPOCH + Duration::from_secs(784887151);
-        let email = Message::builder()
-            .date(date)
-            .bcc("hidden@example.com".parse().unwrap())
-            .header(header::From(
-                vec![Mailbox::new(
-                    Some("Каи".into()),
-                    "kayo@example.com".parse().unwrap(),
-                )]
-                .into(),
-            ))
-            .header(header::To(
-                vec!["Pony O.P. <pony@domain.tld>".parse().unwrap()].into(),
-            ))
-            .header(header::Subject::from(String::from("яңа ел белән!")))
-            .body(String::from("Happy new year!"))
-            .unwrap();
-        let (builder, body) = email.clone().into_parts();
-        let reconstructed = builder.body(body).unwrap();
-        assert_eq!(
-            String::from_utf8(email.formatted()).unwrap(),
-            String::from_utf8(reconstructed.formatted()).unwrap(),
-        );
-    }
 }