macaroons: reject unknown macaroon versions

We've only ever made macaroons with the v2 versions, so we should
explicitly reject those that aren't actually v2. We add a basic test
along the way, and also add a similar check for the version encoded in
the macaroon ID.

macaroons/constraints_test.go

@@ -30,6 +30,8 @@ func createDummyMacaroon(t *testing.T) *macaroon.Macaroon {
 // TestAddConstraints tests that constraints can be added to an existing
 // macaroon and therefore tighten its restrictions.
 func TestAddConstraints(t *testing.T) {
+	t.Parallel()
+
 	// We need a dummy macaroon to start with. Create one without
 	// a bakery, because we mock everything anyway.
 	initialMac := createDummyMacaroon(t)
@@ -55,6 +57,8 @@ func TestAddConstraints(t *testing.T) {
 // TestTimeoutConstraint tests that a caveat for the lifetime of
 // a macaroon is created.
 func TestTimeoutConstraint(t *testing.T) {
+	t.Parallel()
+
 	// Get a configured version of the constraint function.
 	constraintFunc := macaroons.TimeoutConstraint(3)
 
@@ -79,6 +83,8 @@ func TestTimeoutConstraint(t *testing.T) {
 // TestTimeoutConstraint tests that a caveat for the lifetime of
 // a macaroon is created.
 func TestIpLockConstraint(t *testing.T) {
+	t.Parallel()
+
 	// Get a configured version of the constraint function.
 	constraintFunc := macaroons.IPLockConstraint("127.0.0.1")
 
@@ -99,6 +105,8 @@ func TestIpLockConstraint(t *testing.T) {
 // TestIPLockBadIP tests that an IP constraint cannot be added if the
 // provided string is not a valid IP address.
 func TestIPLockBadIP(t *testing.T) {
+	t.Parallel()
+
 	constraintFunc := macaroons.IPLockConstraint("127.0.0/800")
 	testMacaroon := createDummyMacaroon(t)
 	err := constraintFunc(testMacaroon)
@@ -110,6 +118,8 @@ func TestIPLockBadIP(t *testing.T) {
 // TestCustomConstraint tests that a custom constraint with a name and value can
 // be added to a macaroon.
 func TestCustomConstraint(t *testing.T) {
+	t.Parallel()
+
 	// Test a custom caveat with a value first.
 	constraintFunc := macaroons.CustomConstraint("unit-test", "test-value")
 	testMacaroon := createDummyMacaroon(t)