Collect streaming request bodies (#23)

Fixes #22.

Request bodies of a certain size come in streaming and the properties
return `nil`. We should check this and perform a check similar to what
Vapor's routing tools do internally:

1d53c99b6e/Sources/Vapor/Routing/RoutesBuilder%2BMethod.swift (L152)

Sources/VaporRouting/VaporRouting.swift

@@ -32,6 +32,11 @@ where Router.Input == URLRequestData {
     chainingTo next: AsyncResponder
   ) async throws -> Response {
 
+    if request.body.data == nil {
+      try await _ = request.body.collect(max: request.application.routes.defaultMaxBodySize.value)
+        .get()
+    }
+
     guard let requestData = URLRequestData(request: request)
     else { return try await next.respond(to: request) }