DocFix: Replace http_status with status_code

[preet-dev]

Why the changes in this PR are needed?

In the envoy primer doc there are 2 different field names for the optional status_code to be sent when the request is rejected. In the example policy with additional controls it is status_code while in output document it is mentioned as http_status. The former is the correct one.

What are the changes in this PR?

Document change in the envoy policy primer doc to fix the field name for status code to be sent when request is rejected.

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[johanfylling]

Thank you for your contribution @preet-dev! 😃
Would you mind linking to the relevant envoy documentation specifying status_code as the correct field?

[preet-dev]

@johanfylling On this section of the doc (https://www.openpolicyagent.org/docs/latest/envoy-primer/#example-policy-with-additional-controls) it is mentioned as status_code which is correct. However, right below that, in the output document section (https://www.openpolicyagent.org/docs/latest/envoy-primer/#output-document) it is mentioned as http_status.

I actually ended up trying with http_status but that did not work so a more thorough read of the page revealed the right answer for me.

[ashutosh-narkar]

@preet-dev thanks for looking into this. If you notice the result object in https://www.openpolicyagent.org/docs/latest/envoy-primer/#output-document, it mentions that a key called http_status is expected in the policy decision. status_code is just used as a variable name in the example policy but the policy decision object should have a key called http_status. Here is relevant code for reference.