SET client_min_messages TO DEBUG1;
CREATE SERVER osm_http_auth 
FOREIGN DATA WRAPPER nominatim_fdw 
OPTIONS (url 'http://172.19.42.102:3128');
CREATE USER MAPPING FOR postgres
SERVER osm_http_auth OPTIONS (user 'nominatimuser', password 'nominatimpass');
/* must return HTTP 200 */
SELECT osm_id, display_name
FROM nominatim_search(
      server_name => 'osm_http_auth',
      q => 'einsteinstraße 60, münster, germany');
DEBUG:  GET "http://172.19.42.102:3128/search?q=einsteinstra%C3%9Fe%2060%2C%20m%C3%BCnster%2C%20germany&format=xml&accept-language=en-US%2Cen%3Bq%3D0.9&bounded=0"
DEBUG:  HTTP 200, 14 bytes
ERROR:  ParseNominatimSearchData -> request failed: 'http://172.19.42.102:3128'
ALTER USER MAPPING FOR postgres
SERVER osm_http_auth OPTIONS (SET user 'foo', SET password 'bar');
/* invalid credentials, must fail (HTTP 401) */
SELECT osm_id, display_name
FROM nominatim_search(
      server_name => 'osm_http_auth',
      q => 'einsteinstraße 60, münster, germany');
DEBUG:  GET "http://172.19.42.102:3128/search?q=einsteinstra%C3%9Fe%2060%2C%20m%C3%BCnster%2C%20germany&format=xml&accept-language=en-US%2Cen%3Bq%3D0.9&bounded=0"
ERROR:  The requested URL returned error: 401
DETAIL:  URL: "http://172.19.42.102:3128/search?q=einsteinstra%C3%9Fe%2060%2C%20m%C3%BCnster%2C%20germany&format=xml&accept-language=en-US%2Cen%3Bq%3D0.9&bounded=0"
HINT:  Check your request parameters and credentials, if applicable, and try again.
DROP SERVER osm_http_auth CASCADE;
NOTICE:  drop cascades to user mapping for postgres on server osm_http_auth