Better capture "invalid body" errors in the Request or the Response.

[shulard]

Is your feature request related to a problem? Please describe.

Today it's really hard to find where an invalid body error occurs. We must be able to expose the corresponding body to diagnose the issue.
Today we got a simple:

Something went wrong: JSON parsing failed with "Syntax error" for Request

Describe the solution you'd like

Attaching the message which has a failed body to the exception so we might use it to display relevant details to the user.