implement Display for Tag entities rather than to_string

MODELS.md

@@ -77,9 +77,10 @@ impl Tag {
             name,
         }
     }
-
-    pub fn to_string(&self) -> String {
-        format!("Tag({}::tag::{})", &self.host, &self.name)
+}
+impl fmt::Display for Tag {
+    fn format(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}::tag::{}", self.host.as_ref(), self.name.as_ref())
     }
 }
 ```