Feature request: enable retrieval of the entire query

Following conversation with the AWS Support Team, I was advised to open an issue to request the following.

**Request**
Allow for Appsync to return an entire GraphQL query from the `context`.

**Current state**
According to the Info section in the [documentation](https://docs.aws.amazon.com/appsync/latest/devguide/resolver-context-reference.html), the `$context.info.selectionSetGraphQL` value should return the entire query, however it only returns a selection of it.

The Support Team confirmed that _there is no supported mechanism to get the entire query today_.

**Why am I requesting this**
I would like to proxy queries from one Appsync endpoint to another.

[Refer also to thread in the Discussion Forum for AWS Appsync](https://forums.aws.amazon.com/thread.jspa?threadID=343967).

Start with the documented context.info.selectionSetGraphQL behavior in the AWS AppSync resolver context reference and review the linked AWS AppSync Discussion Forum thread. Confirm the gap between the documented and actual query contents, then define what context access must expose so a query can be proxied to another AppSync endpoint.

Written by the indexing model from the issue text.