Grants read-only access after import

Adds execution of grant statements to provide read-only privileges
for the web user following table creation or via a dedicated function.
Facilitates easier post-import permission management.

src/nominatim_db/tools/database_import.py

@@ -157,6 +157,8 @@ def create_tables(conn: Connection, config: Configuration, reverse_only: bool =
 
     sql.run_sql_file(conn, 'tables.sql')
 
+    sql.run_sql_file(conn, 'grants.sql')
+
 
 def create_table_triggers(conn: Connection, config: Configuration) -> None:
     """ Create the triggers for the tables. The trigger functions must already