Add a new table to describe the history of derivations

There's already the package_versions_by_guix_revision_range table, but I think
it would be also useful to be able to see how derivations change over time.

sqitch/deploy/package_derivations_by_guix_revision_range.sql

@@ -0,0 +1,17 @@
+-- Deploy guix-data-service:package_derivations_by_guix_revision_range to pg
+
+BEGIN;
+
+CREATE TABLE package_derivations_by_guix_revision_range (
+  git_repository_id integer NOT NULL REFERENCES git_repositories (id),
+  branch_name varchar NOT NULL,
+  package_name varchar NOT NULL,
+  package_version varchar NOT NULL,
+  derivation_id integer NOT NULL,
+  system varchar NOT NULL,
+  target varchar NOT NULL,
+  first_guix_revision_id integer NOT NULL REFERENCES guix_revisions (id),
+  last_guix_revision_id integer NOT NULL REFERENCES guix_revisions (id)
+);
+
+COMMIT;