zaus

Converts external submission from <a href="https://wordpress.org/plugins/forms-3rdparty-integration/" rel="ugc">Forms: 3rdparty Integration</a> plugin to an XML or JSON post; optionally can add custom headers (to allow SOAP submissions) or transform/combine separate fields into nested values.
This plugin can turn the 3rdparty mappings into XML elements, so that each form post will be the value (or attribute) of an XML element.

Forms: 3rd-Party Xml Post

Converts submission from Forms 3rdparty Integration to xml/json, add headers, or nest fields.

Exposes file upload/attachments to the regular service mapping of <a href="https://wordpress.org/plugins/forms-3rdparty-integration/" rel="ugc">Forms 3rdparty Integration</a>.
From discussion at https://github.com/zaus/forms-3rdparty-integration/issues/40.

Forms: 3rd-Party File Attachments

Add file upload processing to Forms 3rdparty Integration.

Forms: 3rd-Party Xml Post vs Forms: 3rd-Party File Attachments