Kong does not recognized request body property if set to true and if request body exceeds 10000 characters

- `docs.konghq.com` url(s):

### Summary

We are using Kong 1.5 version and request the validator plugin. We have defined the request-validator plugin with the request body property as the required parameter. If the incoming request body size exceeds around 10200 characters, Kong fails to identify the given property in the request. It gives 400 error with error message XYZ property is required.

No files, tests, or entry points are identified. Start by reproducing the request-validator behavior in Kong 1.5 with a request body over about 10,200 characters and a required property; done means the property is recognized instead of producing the reported required-property error.

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