Rework the builds and build_status tables as well as related code

Allow for build status information to be submitted by POST request. This
required some changes to the builds and build_status tables, as for example,
the Cuirass build id may not be available, and the derivation may not be know
yet, so just record the derivation file name.

sqitch/deploy/rework_builds.sql

@@ -0,0 +1,21 @@
+-- Deploy guix-data-service:rework_builds to pg
+
+BEGIN;
+
+DROP TABLE build_status;
+DROP TABLE builds;
+
+CREATE TABLE builds (
+    id integer PRIMARY KEY GENERATED ALWAYS AS IDENTITY,
+    build_server_id integer NOT NULL REFERENCES build_servers(id),
+    derivation_file_name varchar NOT NULL
+);
+
+CREATE TABLE build_status (
+    id integer PRIMARY KEY GENERATED ALWAYS AS IDENTITY,
+    build_id integer NOT NULL REFERENCES builds(id),
+    "timestamp" timestamp without time zone DEFAULT clock_timestamp() NOT NULL,
+    status guix_data_service.buildstatus NOT NULL
+);
+
+COMMIT;

sqitch/revert/rework_builds.sql

@@ -0,0 +1,7 @@
+-- Revert guix-data-service:rework_builds from pg
+
+BEGIN;
+
+-- XXX Add DDLs here.
+
+COMMIT;

sqitch/sqitch.plan

@@ -28,3 +28,4 @@ remove_guix_revision_duplicates 2019-10-05T08:00:14Z Christopher Baines <mail@cb
 package_derivations_by_guix_revision_range 2019-11-09T19:09:48Z Christopher Baines <mail@cbaines.net> # Add package_derivations_by_guix_revision_range
 channel_news_tables 2019-11-15T07:32:07Z Christopher Baines <mail@cbaines.net> # Add tables to store channel news
 build_server_token_seeds 2019-11-23T09:26:48Z Christopher Baines <mail@cbaines.net> # Add build_server_token_seeds table
+rework_builds 2019-11-23T20:41:20Z Christopher Baines <mail@cbaines.net> # Rework the build tables

sqitch/verify/rework_builds.sql

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