where argument support for computed column (that have arguments)

I'd like to be able to filter out results in a gql query based on a computed field.

For example:
Assuming a computed field called searchScore which returns a real value indicating how close a match this record is..

```CREATE OR REPLACE FUNCTION public.person_search_score(p persons, searchtext text) RETURNS real```

```
query MyQuery($searchText: String!) {
persons(where: {searchScore: {_gt: 1}}) {
id
first_name
last_name
nickname
searchScore(args: {searchtext:$searchText})
}
}

```

Read the issue's computed-field example and the GraphQL `where` argument behavior for computed fields. Determine how arguments supplied to `searchScore` should be applied when filtering by that field; done means a query can filter `persons` using the computed field with its arguments, while still returning the requested field value.

Written by the indexing model from the issue text.