✨ feat(gmail_client): add date to message summary

- add date field to MessageSummary struct
- implement methods to set and retrieve the date
- implement method to list the date and subject

src/gmail_client/message_summary.rs

@@ -1,6 +1,7 @@
 #[derive(Debug, Clone)]
 pub struct MessageSummary {
     id: String,
+    date: Option<String>,
     subject: Option<String>,
 }
 
@@ -8,6 +9,7 @@ impl MessageSummary {
     pub(crate) fn new(id: &str) -> Self {
         MessageSummary {
             id: id.to_string(),
+            date: None,
             subject: None,
         }
     }
@@ -27,4 +29,29 @@ impl MessageSummary {
             "*** No Subject for Message ***"
         }
     }
+
+    pub(crate) fn set_date(&mut self, date: &str) {
+        self.date = Some(date.to_string())
+    }
+
+    pub(crate) fn date(&self) -> &str {
+        if let Some(d) = &self.date {
+            d
+        } else {
+            "*** No Date for Message ***"
+        }
+    }
+
+    pub(crate) fn list_date_and_subject(&self) -> String {
+        let Some(date) = self.date.as_ref() else {
+            return "***invalid date or subject***".to_string();
+        };
+
+        let Some(subject) = self.subject.as_ref() else {
+            return "***invalid date or subject***".to_string();
+        };
+        let s = date[5..16].to_string();
+        let s = format!("{s}: {subject}");
+        s
+    }
 }