dvMiddlewareKeysAtRequest top-level constant
Keys the generated request prelude enforces, not the chain.
A body limit cannot be a middleware in the ordinary sense. The chain runs around the handler, and by the time it has anything to say the body has been read -- a limit that arrives after the read is not a limit. So the generator emits the check where the reading happens, and these are declared here so the chain skips them rather than refusing the build.
Implementation
const Set<String> dvMiddlewareKeysAtRequest = <String>{
'bodyLimit',
'uploadLimit',
};