[draft] bug: raise duplicate field name validation error when config generator json/yml has duplicate field name.

[laststylebender14]

When using the Tailcall configuration generator with the following configuration:

{
  "inputs": [
    {
      "curl": {
        "src": "https://jsonplaceholder.typicode.com/posts",
        "fieldName": "posts"
      }
    },
    {
      "curl": {
        "src": "https://jsonplaceholder.typicode.com/todos",
        "fieldName": "posts"
      }
    }
  ],
  "output": {
    "path": "./output.graphql",
    "format": "graphQL"
  },
  "schema": {
    "query": "Query"
  }
}

The generated GraphQL schema is:

type Query {
  posts: [T2] @http(baseURL: "https://jsonplaceholder.typicode.com", path: "/todos")
}

Problem:

The issue is that both https://jsonplaceholder.typicode.com/posts and https://jsonplaceholder.typicode.com/todos use the same fieldName, resulting in only one field being present in the Query type. This causes the field for https://jsonplaceholder.typicode.com/posts to be overwritten by the field for https://jsonplaceholder.typicode.com/todos, leading to incorrect or incomplete schema representation.

Expected Behavior:

If the fieldName is duplicated within the configuration, a validation error should be raised. This will ensure that each field name is unique and prevent incorrect or incomplete schema generation.