feature: Allow Custom HTTP routes and preprocessors to handle binary uploads

[gcleaves]

I have a flow which processes a file and returns some data about the file. At the moment the flow takes base64 input. But I'd like to see if I can decrease the upload size by allowing a binary upload instead of having to use base64 text. The goal is also to improve the endpoint consumer's experience so they can use a tool like Postman or Curl without first needing to convert the file to base64.

Maybe the acceptable content-type could be set in the Custom HTTP route and it passes the raw body to the preprocessor.

Copied from discussion #4470

[gcleaves]

Olé!

[hugocasa]

@gcleaves we now support multipart/form-data directly
the files will be uploaded to s3 and you will get the path

[gcleaves]

Glad to see my use case makes sense. Thanks!