add normalised country name to word table

Country tokens now follow the usual convetion of having the
normalized version in the word column and the extra info about the
country code in the info column.

src/nominatim_api/search/db_search_fields.py

@@ -244,6 +244,21 @@ class SearchData:
 
             setattr(self, field, wstrs)
 
+    def set_countries(self, tokens: List[Token]) -> None:
+        """ Set the WeightedStrings properties for countries. Multiple
+            entries for the same country are deduplicated and the minimum
+            penalty is used. Adapts the global penalty, so that the
+            minimum penalty is 0.
+        """
+        if tokens:
+            min_penalty = min(t.penalty for t in tokens)
+            self.penalty += min_penalty
+            countries: dict[str, float] = {}
+            for t in tokens:
+                cc = t.get_country()
+                countries[cc] = min(t.penalty - min_penalty, countries.get(cc, 10000))
+            self.countries = WeightedStrings(list(countries.keys()), list(countries.values()))
+
     def set_qualifiers(self, tokens: List[Token]) -> None:
         """ Set the qulaifier field from the given tokens.
         """