form paramters vs attachment properties

Content

We have 1 integration to upload a file in Object Internal Storage Of IDCS. This endpoint accepts multipart/form-data. How ever different documents have different approaches to this .

We have a single file which is not multipart and want to upload into target endpoint which acccepts multipart/form-data.

According to this 

https://docs.oracle.com/en/cloud/paas/identity-cloud/17.4.2/rest-api/op-storage-v1-Files-post.html

This is expecting form parameters. 

(contentType, file, fileName  - populating base64 content to file)

According to this 

https://docs.oracle.com/en/cloud/paas/integration-cloud/rest-adapter/map-construct-payload-external-rest-api-that-accepts-multipart-form-data-content-type.html

this is expecting attachment properties to be filled in.