hotfix(portforward): log both external and internal ports when they diverge

- useful for ProtonVPN only
- clarify things up for the user

internal/portforward/service/helpers_test.go

@@ -40,3 +40,42 @@ func Test_portsToString(t *testing.T) {
 		})
 	}
 }
+
+func Test_externalInternalPortsToString(t *testing.T) {
+	t.Parallel()
+
+	testCases := map[string]struct {
+		internalToExternalPort map[uint16]uint16
+		s                      string
+	}{
+		"no_port": {
+			s: "no port forwarded",
+		},
+		"one_port": {
+			internalToExternalPort: map[uint16]uint16{123: 123},
+			s:                      "port forwarded is 123",
+		},
+		"two_ports": {
+			internalToExternalPort: map[uint16]uint16{123: 123, 456: 456},
+			s:                      "ports forwarded are 123 and 456",
+		},
+		"two_ports_different_internal_external": {
+			internalToExternalPort: map[uint16]uint16{123: 124, 456: 457},
+			s:                      "ports forwarded are 124 (internal port 123) and 457 (internal port 456)",
+		},
+		"three_ports": {
+			internalToExternalPort: map[uint16]uint16{123: 123, 456: 456, 789: 789},
+			s:                      "ports forwarded are 123, 456 and 789",
+		},
+	}
+
+	for name, testCase := range testCases {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			s := portPairsToString(testCase.internalToExternalPort)
+
+			assert.Equal(t, testCase.s, s)
+		})
+	}
+}