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/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