Add From<Mime> under mime03 flag (#676)

Closes #615

Cargo.toml

@@ -78,6 +78,7 @@ name = "transport_smtp"
 [features]
 default = ["smtp-transport", "pool", "native-tls", "hostname", "r2d2", "builder"]
 builder = ["httpdate", "mime", "base64", "fastrand", "quoted_printable"]
+mime03 = ["mime"]
 
 # transports
 file-transport = ["uuid"]

src/lib.rs

@@ -85,16 +85,19 @@
 //!
 //! * **serde**: Serialization/Deserialization of entities
 //! * **tracing**: Logging using the `tracing` crate
+//! * **mime03**: Allow creating a [`ContentType`] from an existing [mime 0.3] `Mime` struct
 //!
 //! [`SMTP`]: crate::transport::smtp
 //! [`sendmail`]: crate::transport::sendmail
 //! [`file`]: crate::transport::file
+//! [`ContentType`]: crate::message::header::ContentType
 //! [tokio]: https://docs.rs/tokio/1
 //! [async-std]: https://docs.rs/async-std/1
 //! [ring]: https://github.com/briansmith/ring#ring
 //! [ring-support]: https://github.com/briansmith/ring#online-automated-testing
 //! [Tokio 1.x]: https://docs.rs/tokio/1
 //! [async-std 1.x]: https://docs.rs/async-std/1
+//! [mime 0.3]: https://docs.rs/mime/0.3
 
 #![doc(html_root_url = "https://docs.rs/crate/lettre/0.10.0-rc.3")]
 #![doc(html_favicon_url = "https://lettre.rs/favicon.ico")]

src/message/header/content_type.rs

@@ -67,6 +67,14 @@ impl FromStr for ContentType {
     }
 }
 
+#[cfg(feature = "mime03")]
+#[cfg_attr(docsrs, doc(cfg(feature = "mime03")))]
+impl From<Mime> for ContentType {
+    fn from(mime: Mime) -> Self {
+        Self::from_mime(mime)
+    }
+}
+
 /// An error occurred while trying to [`ContentType::parse`].
 #[derive(Debug)]
 pub struct ContentTypeErr(mime::FromStrError);