Rework request

[lgebhardt]

Renames JSONAPI::RequestParser to JSONAPI::Request and provides access to this in the controller by a class variable. This will provide access to the request for inspection and manipulation in the process_operations callbacks.

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• Maintains compliance with JSON:API
• Adequate test coverage exists to prevent regressions

[dgeb]

Looks good! I like the naming refactor as well as the switch to setting up an array of @operations.