Lacking documentation on mixed text/binary payloads for http proxy integration

[Lux-CC]

On this page it's stated that In API Gateway, the API request and response have a text or binary payload. A text payload is a UTF-8-encoded JSON string. A binary payload is anything other than a text payload. However, this leaves ambiguity in trying to set up an integration for multipart/form-data, which is essentially a mixture of the two.

Also, the page is lacking documentation for non-lambda proxy integrations (http_proxy). It only talks about lambda proxy and non-proxy integrations.