python: implement reverse lookup function

The implementation follows for most part the PHP code but introduces an
additional layer parameter with which the kind of places to be returned
can be restricted. This replaces the hard-coded exclusion lists.

nominatim/api/results.py

@@ -46,8 +46,6 @@ class AddressLine:
     names: Dict[str, str]
     extratags: Optional[Dict[str, str]]
 
-    local_name: Optional[str] = None
-
     admin_level: Optional[int]
     fromarea: bool
     isaddress: bool
@@ -81,7 +79,6 @@ class BaseResult:
 
     place_id : Optional[int] = None
     osm_object: Optional[Tuple[str, int]] = None
-    admin_level: int = 15
 
     names: Optional[Dict[str, str]] = None
     address: Optional[Dict[str, str]] = None
@@ -135,6 +132,7 @@ class DetailedResult(BaseResult):
     """
     parent_place_id: Optional[int] = None
     linked_place_id: Optional[int] = None
+    admin_level: int = 15
     indexed_date: Optional[dt.datetime] = None
 
 
@@ -164,7 +162,6 @@ def create_from_placex_row(row: Optional[SaRow],
                       place_id=row.place_id,
                       osm_object=(row.osm_type, row.osm_id),
                       category=(row.class_, row.type),
-                      admin_level=row.admin_level,
                       names=row.name,
                       address=row.address,
                       extratags=row.extratags,