Naming, layout and comments: descriptive full-word names, one item per line in wrapped calls and literals, and doc comments on exported names

Short and single-letter names in application code become full words (tests
keep theirs). Wrapped calls, signatures and composite literals put one item
per line, and one-line function bodies are expanded. Exported names and
groups of constants get doc comments, and comments refer to the renamed
identifiers.

internal/store/queries_test.go

@@ -84,7 +84,9 @@ func openTestDB(t *testing.T) *sqlx.DB {
 	if err != nil {
 		t.Fatalf("Open: %v", err)
 	}
-	t.Cleanup(func() { s.Close() })
+	t.Cleanup(func() {
+		s.Close()
+	})
 	return s.db
 }