change updates to handle delete/insert workflow

This makes Nominatim compatible with osm2pgsql's default update
modus operandi of deleting and reinserting data. Deletes are diverted
into a TODO table instead of executing them. When data is reinserted,
the corresponding entry in the TODO table is deleted. After updates are
finished, the remaining entries in the TODO table are executed, doing
the same work as the delete trigger did before.

The new behaviour also works against the gazetteer output with its
insert-only mechanism.

test/bdd/steps/steps_osm_data.py

@@ -10,6 +10,7 @@ import os
 from pathlib import Path
 
 from nominatim.tools.exec_utils import run_osm2pgsql
+from nominatim.tools.replication import run_osm2pgsql_updates
 
 from geometry_alias import ALIASES
 
@@ -118,6 +119,7 @@ def update_from_osm_file(context):
     # create an OSM file and import it
     fname = write_opl_file(context.text, context.osm)
     try:
-        run_osm2pgsql(get_osm2pgsql_options(context.nominatim, fname, append=True))
+        run_osm2pgsql_updates(context.db,
+                              get_osm2pgsql_options(context.nominatim, fname, append=True))
     finally:
         os.remove(fname)