test: sanity tests for primary and replica

* new --replica option to `postgrest-with-postgresql-*`
* new command `postgrest-test-replica`
* new sanity tests on test_replica.py
* add postgrest-test-replica to postgrest-check and postgrest-coverage

test/io/replica.sql

@@ -0,0 +1,21 @@
+create schema replica;
+
+create or replace function replica.is_replica() returns bool as $$
+  select pg_is_in_recovery();
+$$ language sql;
+
+create or replace function replica.get_replica_slot() returns name as $$
+  select slot_name from pg_replication_slots limit 1;
+$$ language sql;
+
+create table replica.items as select x as id from generate_series(1, 10) x;
+
+DROP ROLE IF EXISTS postgrest_test_anonymous;
+CREATE ROLE postgrest_test_anonymous;
+
+GRANT postgrest_test_anonymous TO :PGUSER;
+
+GRANT USAGE ON SCHEMA replica TO postgrest_test_anonymous;
+
+GRANT ALL PRIVILEGES ON ALL TABLES IN SCHEMA replica
+TO postgrest_test_anonymous;