✨ feat(eol_cmd): introduce EolCmd enum for message disposal

- add Trash and Delete variants for specifying end-of-life actions
- implement Display trait for EolCmd to provide string representation

src/eol_cmd.rs

@@ -0,0 +1,22 @@
+use std::fmt;
+
+/// End of life command
+/// - Trash - move the message to the trash to be automatically deleted by Google
+/// - Delete - delete the message immediately without allowing rescue from trash
+#[derive(Debug, Default)]
+pub enum EolCmd {
+    #[default]
+    /// Move the message to the trash
+    Trash,
+    /// Delete the message immediatly
+    Delete,
+}
+
+impl fmt::Display for EolCmd {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            EolCmd::Trash => write!(f, "trash"),
+            EolCmd::Delete => write!(f, "delete"),
+        }
+    }
+}