add get cities handler and improve db schema

service_a/server/database/migrations/001_data.up.sql

@@ -1,4 +1,10 @@
 create extension citext; -- noqa
+create extension unaccent;
+
+create or replace function immutable_unaccent(text)
+returns text as $$
+  select unaccent('unaccent', $1);
+$$ language sql immutable;
 
 create table public.ingest_batch
 (
@@ -20,6 +26,7 @@ create table public.meteo_data
     batch_id int not null references public.ingest_batch (id),
 
     location_name citext not null,
+    location_name_norm text generated always as (immutable_unaccent(lower(location_name))) stored,
     date_of_register date not null,
     max_temp numeric(5, 2) not null,
     min_temp numeric(5, 2) not null,
@@ -29,7 +36,7 @@ create table public.meteo_data
     created_at timestamp not null default now()
 );
 
-create index idx_meteo_data_location_name on public.meteo_data (location_name);
+create index idx_meteo_data_location_name_norm on public.meteo_data (location_name_norm);
 
 create table public.rejected_data
 (