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/mock/findatender/handler_test.go

@@ -79,7 +79,9 @@ func openTestStore(t *testing.T) *Store {
 	if err != nil {
 		t.Fatal(err)
 	}
-	t.Cleanup(func() { store.Close() })
+	t.Cleanup(func() {
+		store.Close()
+	})
 	return store
 }
 
@@ -92,7 +94,9 @@ func TestHandlerRejectsBadRequests(t *testing.T) {
 		t.Errorf("POST: status %d, want 405", rec.Code)
 	}
 
-	cursor := func(s string) string { return base64.RawURLEncoding.EncodeToString([]byte(s)) }
+	cursor := func(s string) string {
+		return base64.RawURLEncoding.EncodeToString([]byte(s))
+	}
 	cases := map[string]string{
 		"limit=0":               "limit must be an integer between 1 and 100",
 		"limit=101":             "limit must be an integer between 1 and 100",