Add Wisun Fan device certificate

Add certificate with Wisun fan device extended key usage,
support parsing it and add tests.
diff --git a/tests/data_files/server5-fan.crt b/tests/data_files/server5-fan.crt
new file mode 100644
index 0000000..dc1eb38
--- /dev/null
+++ b/tests/data_files/server5-fan.crt
@@ -0,0 +1,10 @@
+-----BEGIN CERTIFICATE-----
+MIIBdTCCARugAwIBAgIBTTAKBggqhkjOPQQDAjA3MQswCQYDVQQGEwJVSzERMA8G
+A1UECgwITWJlZCBUTFMxFTATBgNVBAMMDE1iZWQgVExTIEZBTjAeFw0xOTAzMjUw
+OTAzNDZaFw0yOTAzMjIwOTAzNDZaMDcxCzAJBgNVBAYTAlVLMREwDwYDVQQKDAhN
+YmVkIFRMUzEVMBMGA1UEAwwMTWJlZCBUTFMgRkFOMFkwEwYHKoZIzj0CAQYIKoZI
+zj0DAQcDQgAEN8xW2XYJHlpyPsdZLf8gbu58+QaRdNCtFLX3aCJZYpJO5QDYIxH/
+6i/SNF1dFr2KiMJrdw1VzYoqDvoByLTt/6MYMBYwFAYDVR0lBA0wCwYJKwYBBAGC
+5CUBMAoGCCqGSM49BAMCA0gAMEUCIQDp/Q5FaVy3YNeJflQKLGycQZoH6V3FQnLq
+ERUCeimLIAIgdyiA4KdHxkpQhC1L1KfmxG8YJqu31FBjmNw00Sv8J9k=
+-----END CERTIFICATE-----