Issue when migrating to okhttp3

[Kenji94]

Error stacktrace:
java.lang.UnsupportedOperationException: null
at java.base/java.util.Collections$UnmodifiableCollection.add(Collections.java:1067)
at sibApi.ContactsApi.createContactCall(ContactsApi.java:389)
at sibApi.ContactsApi.createContactValidateBeforeCall(ContactsApi.java:413)
at sibApi.ContactsApi.createContactAsync(ContactsApi.java:472)

Solution:
square/okhttp#2219