initial postcode cleaner for simple patterns

Moves postcodes that are either in countries without a postcode
system or don't correspond to the local pattern for postcodes into
a field for a normal address part. Makes them searchable but not as
a special address. This has two consequences: they are no longer a
skippable part of the address and the postcodes cannot be searched
on their own.

test/python/tokenizer/sanitizers/test_clean_postcodes.py

@@ -0,0 +1,54 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# This file is part of Nominatim. (https://nominatim.org)
+#
+# Copyright (C) 2022 by the Nominatim developer community.
+# For a full list of authors see the git log.
+"""
+Tests for the sanitizer that normalizes postcodes.
+"""
+import pytest
+
+from nominatim.tokenizer.place_sanitizer import PlaceSanitizer
+from nominatim.indexer.place_info import PlaceInfo
+from nominatim.tools import country_info
+
+@pytest.fixture
+def sanitize(def_config, request):
+    country_info.setup_country_config(def_config)
+    sanitizer_args = {'step': 'clean-postcodes'}
+    for mark in request.node.iter_markers(name="sanitizer_params"):
+        sanitizer_args.update({k.replace('_', '-') : v for k,v in mark.kwargs.items()})
+
+    def _run(country=None, **kwargs):
+        pi = {'address': kwargs}
+        if country is not None:
+            pi['country_code'] = country
+
+        _, address = PlaceSanitizer([sanitizer_args]).process_names(PlaceInfo(pi))
+
+        return sorted([(p.kind, p.name) for p in address])
+
+    return _run
+
+
+@pytest.mark.parametrize("country", (None, 'ae'))
+def test_postcode_no_country(sanitize, country):
+    assert sanitize(country=country, postcode='23231') == [('unofficial_postcode', '23231')]
+
+
+@pytest.mark.parametrize("country", (None, 'ae'))
+@pytest.mark.sanitizer_params(convert_to_address=False)
+def test_postcode_no_country_drop(sanitize, country):
+    assert sanitize(country=country, postcode='23231') == []
+
+
+@pytest.mark.parametrize("postcode", ('12345', '  34009  '))
+def test_postcode_pass_good_format(sanitize, postcode):
+    assert sanitize(country='de', postcode=postcode) == [('postcode', postcode.strip())]
+
+
+@pytest.mark.parametrize("postcode", ('123456', '', '   ', '.....'))
+@pytest.mark.sanitizer_params(convert_to_address=False)
+def test_postcode_drop_bad_format(sanitize, postcode):
+    assert sanitize(country='de', postcode=postcode) == []