Duplicate codegenContents when requestBody has multiple content types and one of them is a form

[alf-mindshift]

Given a resource with multiple content types, the generated code will not compile if one or more of these content types is either application/x-www-form-urlencoded or multipart/form-data.

In the case where the requestBody is identical, the following fix seems to work. When the request bodies are different, you'll hit #441.