Port short uuid code to Go

tools/utils/short-uuid_test.go

@@ -0,0 +1,28 @@
+// License: GPLv3 Copyright: 2022, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package utils
+
+import (
+	"math/big"
+	"testing"
+)
+
+func TestShortUUID(t *testing.T) {
+	if HumanUUID.pad_to_length != 22 {
+		t.Fatalf("pad length for human UUID is %d not %d", HumanUUID.pad_to_length, 22)
+	}
+	u, err := HumanUUID.Uuid4()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(u) != 22 {
+		t.Fatalf("uuid4 %s has unexpected length: %d", u, len(u))
+	}
+
+	b := big.NewInt(int64(1234567890123456789))
+	q := num_to_string(b, HumanUUID.alphabet, &HumanUUID.alphabet_len, HumanUUID.pad_to_length)
+	const expected = "bzT6LtUjw4422222222222"
+	if q != expected {
+		t.Fatalf("unexpected short human serialization: %s != %s", q, expected)
+	}
+}