Add trip country_flags method

agenda/types.py

@@ -90,6 +90,11 @@ class Trip:
             [f"{c.flag} {c.name}" for c in self.countries]
         )
 
+    @property
+    def country_flags(self) -> str:
+        """Countries flags for trip."""
+        return "".join(c.flag for c in self.countries)
+
 
 @dataclass
 class Holiday: