bug: `@graphql` directive fails to escape strings in nested queries for arguments

[amitksingh1490]

Description

The @graphql directive does not correctly escape string literals in nested queries arguments. This results in invalid JSON strings.

Steps to Reproduce

1. Define a GraphQL query with a nested filter that includes a string equality condition:

   query {
    queryTest(filter: { a: { eq: "A" } }) {
      id
      name(filter: { eq: "A" })
    }
   }

   Actual

   { "query": "query { getMyType(filter: {a: {eq: \"A\"}}) { id name(filter: {eq: "A"}) } }" }

   Expected

   { "query": "query { getMyType(filter: {a: {eq: \"A\"}}) { id name(filter: {eq: \"A\"}) } }" }