zpages: JSON support via Accept header

[wperron]

Problem Statement

I want to be able to easily parse the response from the zpages extension to programatically inspect configuration.

Proposed Solution

Format the response in JSON if the Accept header is set to application/json.

Alternatives

I'm sure it's possible to parse the HTML, but it's cumbersome, whereas all languages support some form of JSON parsing.

Prior Art

Additional Context