[BUG] Misleading error message parsing named params with feature flag disabled

[dbwiddis]

What is the bug?

When attempting to use an API with a named param, the param is not parsed before the check if the API is disabled. This gives a misleading error message to the user.

How can one reproduce the bug?

1. Do not enable the feature flag.
2. Call the create workflow API with ?provision=true
3. Observe error:

{
    "error": {
        "root_cause": [
            {
                "type": "illegal_argument_exception",
                "reason": "request [/_plugins/_flow_framework/workflow] contains unrecognized parameter: [provision]"
            }
        ],
        "type": "illegal_argument_exception",
        "reason": "request [/_plugins/_flow_framework/workflow] contains unrecognized parameter: [provision]"
    },
    "status": 400
}

What is the expected behavior?

{
    "error": "This API is disabled. To enable it, set [plugins.flow_framework.enabled] to true."
}