feat(db): Add table for census upload job status

internal/db/schema/migrations/oss/postgres/72/01_census.up.sql

@@ -0,0 +1,20 @@
+-- Copyright (c) HashiCorp, Inc.
+-- SPDX-License-Identifier: MPL-2.0
+
+begin;
+
+  create table census_last_uploaded (
+    last_uploaded_at wt_timestamp primary key
+  );
+  comment on table census_last_uploaded is
+    'census_last_uploaded is a table with 1 row which contains '
+    'the timestamp of the last time census data was uploaded.';
+
+  -- This index ensures that there will only ever be one row in the table.
+  -- See: https://www.postgresql.org/docs/current/indexes-expressional.html
+  create unique index census_last_uploaded_one_row
+    on census_last_uploaded((last_uploaded_at is not null));
+
+  insert into census_last_uploaded(last_uploaded_at) values('-infinity');
+
+commit;

internal/db/sqltest/Makefile

@@ -27,6 +27,7 @@ TESTS ?= tests/setup/*.sql \
 		 tests/target/*.sql \
 		 tests/controller/*.sql \
 		 tests/hcp/*/*.sql \
+		 tests/census/*.sql \
 		 tests/kms/*.sql \
 		 tests/storage/*.sql \
 		 tests/domain/*.sql \

internal/db/sqltest/tests/census/last_uploaded.sql

@@ -0,0 +1,31 @@
+-- Copyright (c) HashiCorp, Inc.
+-- SPDX-License-Identifier: MPL-2.0
+
+begin;
+
+  select plan(6);
+
+  select has_table('census_last_uploaded');
+  select is(count(*), 1::bigint, 'census_last_uploaded should have only 1 row') from census_last_uploaded;
+  select ok(not isfinite(last_uploaded_at)) from census_last_uploaded;
+
+  prepare insert_row as
+   insert into census_last_uploaded
+    (last_uploaded_at)
+   values
+    (now());
+
+  select throws_ok('insert_row', '23505',
+    'duplicate key value violates unique constraint "census_last_uploaded_one_row"',
+    'insert into census_last_uploaded should fail');
+
+  prepare update_census_last_uploaded as
+   update census_last_uploaded
+      set last_uploaded_at = now();
+
+  select lives_ok('update_census_last_uploaded');
+  select ok(isfinite(last_uploaded_at)) from census_last_uploaded;
+
+  select * from finish();
+
+rollback;