Remove the sha1_hash from the package_metadata table

I'm thinking about adding more fields to this table, and the sha1_hash values
will make this tricker.

Therefore, remove the value, and adjust the existing code to cope. This commit
also adds a new test which coveres some of the changed functionality.

tests/model-package-metadata.scm

@@ -0,0 +1,37 @@
+(define-module (test-model-package-metadata)
+  #:use-module (ice-9 match)
+  #:use-module (srfi srfi-64)
+  #:use-module (tests mock-inferior)
+  #:use-module (guix-data-service database))
+
+(test-begin "test-model-package-metadata")
+
+(define mock-inferior-package-foo
+  (mock-inferior-package
+   (name "foo")
+   (version "2")
+   (synopsis "Foo")
+   (description "Foo description")
+   (home-page "https://example.com")))
+
+(with-mock-inferior-packages
+ (lambda ()
+   (use-modules (guix-data-service model package)
+                (guix-data-service model git-repository)
+                (guix-data-service model guix-revision)
+                (guix-data-service model package-metadata))
+
+   (with-postgresql-connection
+    (lambda (conn)
+      (test-assert "inferior-packages->package-metadata-ids"
+        (with-postgresql-transaction
+         conn
+         (lambda (conn)
+           (match
+               (inferior-packages->package-metadata-ids
+                conn
+                (list mock-inferior-package-foo))
+             ((x) (string? x))))
+         #:always-rollback? #t))))))
+
+(test-end)