How to send a file to external REST service as a body from osb 11g.

I have to send/upload the file to external REST API as a body using POST method in OSB 11g using business service. Here is the service flow.

Source (PGP encrypted File)-->File Location-->Proxy Service(File protocol)-->Pipeline(How to send File as body to REST API)-->Business Service(Invoking external REST endpoint)-->Target (External REST service.)

While testing through POSTMAN: 

In the Header Section: Content-Type is: multipart/form-data

in the Body section  I am selecting : form-data

Key : file

Value: File (pgp encrypted file).

Method: POST

Please let me know how to achieve the same from osb11g. I am currently using OSB 11.1.1.7.0 version. SOA is not available in this project. .