Feature Request: function.json setting to allow additional parameters beyond input bindings

I often want to have parameters defined that aren't input bindings, that may pull from other things such as application settings or azure key vault, and all the rich parameter validation that comes with `Mandatory`, `ValidateNotNullOrEmpty`, etc.

Currently I have to do this in the body of my function which results in a lot of "if" statements to do validation, etc.

There should be a function.json setting which will allow additional parameters beyond the input bindings, but still throw an error if there is a input binding that doesn't have a matching parameter.