api: support multi-character site IDs

now required in practice by the rates+pop injection dataset

gwdatafind/api.py

@@ -63,7 +63,7 @@ def find_types_path(site=None, ext=DEFAULT_EXT):
     """Return the API path to query for datasets for one or all sites.
     """
     if site:
-        return f"{ext}/{site[0]}.json"
+        return f"{ext}/{site}.json"
     return f"{ext}/all.json"