Incorrect HTTP Method in listAttachments() Method

[henriAbel]

Problem
The listAttachments() method in the SDK is utilizing the HTTP POST method while the official documentation for the Invoiced API specifies that the correct method for listing invoice attachments should be HTTP GET.

Error encountered
com.invoiced.exception.EntityException: com.invoiced.exception.ApiException: {"type":"invalid_request","message":"Method not allowed: POST \/invoices\/12967910\/attachments"}