Input object type with union check

Refactor handleWarning() and fillEmptyResponses option defaults to arbitrary JSON type

Signed-off-by: Alan Cha <[email protected]>

Author: Alan-Cha

packages/openapi-to-graphql/README.md

@@ -150,7 +150,7 @@ Schema options:
 
 - `operationIdFieldNames` (type: `boolean`, default: `false`): By default, query field names are based on the return type's type name and mutation field names are based on the [`operationId`](https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.2.md#operation-object), which may be generated if it does not exist. This option forces OpenAPI-to-GraphQL to only create field names based on the operationId.
 
-- `fillEmptyResponses` (type: `boolean`, default: `false`): OpenAPI-to-GraphQL, by default, will only wrap operations that have a [response schema](https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.0.md#responsesObject). Therefore, operations that _do not have_ response schemas will be ignored. The reason is that all GraphQL objects must have a data structure and in these cases where the OAS does not define response schemas, the data structures cannot be safely assumed. As a result, it is recommended that the OAS should be modified to include a response schema. However, under certain circumstances, some operations should _not in fact_ have a response schema. One circumstance is HTTP status code 204, in which no content should be returned. The option `fillEmptyResponses` will allow OpenAPI-to-GraphQL to wrap these operations by assigning these operations a nullable data structure. Although this data structure is meaningless, the operation will appear in the schema.
+- `fillEmptyResponses` (type: `boolean`, default: `false`): OpenAPI-to-GraphQL, by default, will only wrap operations that have a [response schema](https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.0.md#responsesObject). Therefore, operations that _do not have_ response schemas will be ignored. The reason is that all GraphQL objects must have a data structure and in these cases where the OAS does not define response schemas, the data structures cannot be safely assumed. As a result, it is recommended that the OAS should be modified to include a response schema. However, under certain circumstances, some operations should _not in fact_ have a response schema. One circumstance is HTTP status code 204, in which no content should be returned. The option `fillEmptyResponses` will allow OpenAPI-to-GraphQL to wrap these operations by assigning these operations a placeholder data structure. Although this data structure is meaningless, the operation will appear in the schema.
 
 - `addLimitArgument` (type: `boolean`, default: `false`): Add a `limit` argument to fields returning lists of objects/lists that will limit the number of returned elements, selecting the first `n` elements of the list.