email: Add activation_token

Requires version 4.

src/desktop/email.rs

@@ -43,6 +43,7 @@ struct EmailOptions {
     subject: Option<String>,
     body: Option<String>,
     attachment_fds: Option<Vec<Fd>>,
+    activation_token: Option<String>,
 }
 
 #[derive(Debug)]
@@ -167,6 +168,13 @@ impl EmailRequest {
         self
     }
 
+    /// Sets the activation token.
+    #[must_use]
+    pub fn activation_token<'a>(mut self, activation_token: impl Into<Option<&'a str>>) -> Self {
+        self.options.activation_token = activation_token.into().map(ToOwned::to_owned);
+        self
+    }
+
     /// A different variant of [`Self::attach`].
     pub fn add_attachment(&mut self, attachment: &impl AsRawFd) {
         let attachment = Fd::from(attachment.as_raw_fd());