Add a table to record where narinfo files were fetched from

Otherwise it's hard to associated narinfo files to build servers.

sqitch/deploy/narinfo_fetch_record.sql

@@ -0,0 +1,12 @@
+-- Deploy guix-data-service:narinfo_fetch_record to pg
+
+BEGIN;
+
+CREATE TABLE narinfo_fetch_records (
+    id integer PRIMARY KEY GENERATED ALWAYS AS IDENTITY,
+    narinfo_signature_data_id integer NOT NULL REFERENCES narinfo_signature_data(id),
+    build_server_id integer NOT NULL REFERENCES build_servers(id),
+    fetched_at timestamp without time zone DEFAULT clock_timestamp()
+);
+
+COMMIT;

sqitch/revert/narinfo_fetch_record.sql

@@ -0,0 +1,7 @@
+-- Revert guix-data-service:narinfo_fetch_record from pg
+
+BEGIN;
+
+DROP TABLE narinfo_fetch_record;
+
+COMMIT;

sqitch/sqitch.plan

@@ -31,3 +31,4 @@ build_server_token_seeds 2019-11-23T09:26:48Z Christopher Baines <mail@cbaines.n
 rework_builds 2019-11-23T20:41:20Z Christopher Baines <mail@cbaines.net> # Rework the build tables
 nar_related_tables 2019-11-29T20:28:19Z Christopher Baines <mail@cbaines.net> # Add nar related tables
 add_index_on_builds_derivation_file_name 2019-12-03T16:23:55Z   <chris@phact> # Add index on builds_derivation_file_name
+narinfo_fetch_record 2019-12-03T20:53:28Z   <chris@phact> # Add a table to describe fetching a narinfo

sqitch/verify/narinfo_fetch_record.sql

@@ -0,0 +1,7 @@
+-- Verify guix-data-service:narinfo_fetch_record on pg
+
+BEGIN;
+
+-- XXX Add verifications here.
+
+ROLLBACK;