refactor: use string slices

src/email_client.rs

@@ -32,11 +32,11 @@ impl EmailClient {
             .and_then(|path| path.join("email"))
             .unwrap();
         let request_body = SendEmailRequest {
-            from: self.sender.as_ref().to_owned(),
-            to: recipient.as_ref().to_owned(),
-            subject: subject.to_owned(),
-            html_body: html_content.to_owned(),
-            text_body: text_content.to_owned(),
+            from: self.sender.as_ref(),
+            to: recipient.as_ref(),
+            subject,
+            html_body: html_content,
+            text_body: text_content,
         };
         let builder = self
             .http_client
@@ -51,12 +51,12 @@ impl EmailClient {
 
 #[derive(Serialize)]
 #[serde(rename_all = "PascalCase")]
-struct SendEmailRequest {
-    from: String,
-    to: String,
-    subject: String,
-    html_body: String,
-    text_body: String,
+struct SendEmailRequest<'a> {
+    from: &'a str,
+    to: &'a str,
+    subject: &'a str,
+    html_body: &'a str,
+    text_body: &'a str,
 }
 
 #[cfg(test)]