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/Makefile b/tests/data_files/Makefile
index d139bfa..d1af18c 100644
--- a/tests/data_files/Makefile
+++ b/tests/data_files/Makefile
@@ -184,6 +184,9 @@
 server5-unsupported_othername.crt: server5.key
 	$(OPENSSL) req -x509 -new -subj "/C=UK/O=Mbed TLS/CN=Mbed TLS unsupported othername SAN" -set_serial 77 -config $(test_ca_config_file) -extensions unsupoported_othername_san -days 3650 -sha256 -key $< -out $@
 
+server5-fan.crt: server5.key
+	$(OPENSSL) req -x509 -new -subj "/C=UK/O=Mbed TLS/CN=Mbed TLS FAN" -set_serial 77 -config $(test_ca_config_file) -extensions fan_cert -days 3650 -sha256 -key server5.key -out $@
+
 server10-badsign.crt: server10.crt
 	{ head -n-2 $<; tail -n-2 $< | sed -e '1s/0\(=*\)$$/_\1/' -e '1s/[^_=]\(=*\)$$/0\1/' -e '1s/_/1/'; } > $@
 all_final += server10-badsign.crt
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-----
diff --git a/tests/data_files/test-ca.opensslconf b/tests/data_files/test-ca.opensslconf
index 5f71532..d2c5c06 100644
--- a/tests/data_files/test-ca.opensslconf
+++ b/tests/data_files/test-ca.opensslconf
@@ -51,6 +51,9 @@
 policyIdentifier = 2.5.29.32.0
 CPS.1 ="CPS uri string"
 
+[fan_cert]
+extendedKeyUsage = 1.3.6.1.4.1.45605.1
+
 [noext_ca]
 basicConstraints = CA:true