fix: add a comment to the expiryInstant

src/main/java/org/eclipse/tractusx/managedidentitywallets/utils/CommonUtils.java

@@ -115,6 +115,7 @@ private static VerifiableCredential createVerifiableCredential(DidDocument issue
         }
 
         // check if the expiryDate is set
+        // if its null then it will be ignored from the SSI Lib (VerifiableCredentialBuilder) and will not be added to the VC
         Instant expiryInstant = null;
         if (expiryDate != null) {
             expiryInstant = expiryDate.toInstant();