Extracting SubjectKeyId and AuthorityKeyId in case of x509 V3 extensions. Updating mbedtls_x509_crt_free function to also free the new dynamic elements (issuer field of AuthorityKeyId).
A few tests are also added which test the feature with a correct certificate and multiple ones with erroneous ASN1 tags.

Signed-off-by: toth92g <toth92g@gmail.com>
diff --git a/library/oid.c b/library/oid.c
index aa5f69c..732b386 100644
--- a/library/oid.c
+++ b/library/oid.c
@@ -291,7 +291,15 @@
         MBEDTLS_OID_X509_EXT_CERTIFICATE_POLICIES,
     },
     {
-        NULL_OID_DESCRIPTOR,
+        { ADD_LEN(MBEDTLS_OID_SUBJECT_KEY_IDENTIFIER), "id-ce-subjectKeyIdentifier",           "Subject Key Identifier" },
+        MBEDTLS_OID_X509_EXT_SUBJECT_KEY_IDENTIFIER,
+    },
+    {
+        { ADD_LEN(MBEDTLS_OID_AUTHORITY_KEY_IDENTIFIER), "id-ce-authorityKeyIdentifier",       "Authority Key Identifier" },
+        MBEDTLS_OID_X509_EXT_AUTHORITY_KEY_IDENTIFIER,
+    },
+    {
+        { NULL, 0, NULL, NULL },
         0,
     },
 };