InterfaceTypeDefinition should contain "possibleTypes" as returned by introspection

[cooniur]

Library version: v16.1

Describe the bug
TL;DR
For an interface type, the possibleTypes should be captured in InterfaceTypeDefinition by IntrospectionResultToSchema.

Details:
When introspecting an interface type, the introspection result would look like (example taken from this test):

{
  "kind": "INTERFACE",
  "name": "Character",
  "description": "A character in the Star Wars Trilogy",
  "fields": [
    {
      "name": "id",
      "description": "The id of the character.",
      "args": [],
      "type": {
        "kind": "NON_NULL",
        "name": null,
        "ofType": {
          "kind": "SCALAR",
          "name": "String",
          "ofType": null
        }
      },
      "isDeprecated": false,
      "deprecationReason": null
    },
    ...
  ],
  "inputFields": null,
  "interfaces": null,
  "enumValues": null,
  "possibleTypes": [
    {
      "kind": "OBJECT",
      "name": "Human",
      "ofType": null
    },
    {
      "kind": "OBJECT",
      "name": "Droid",
      "ofType": null
    }
  ]
}

The IntrospectionResultToSchema#createSchemaDefinition can parse the introspection result and returns the InterfaceTypeDefinition object. However, the possibleTypes are lost during the parsing. In fact, the InterfaceTypeDefinition class itself does not contain a data structure to capture possible types at all (as compared to the UnionTypeDefinition which contains memberTypes that is used to contain possible types).

This would make it difficult to analyze GraphQL types programmatically because of the missing possible types information.

To Reproduce
Run IntrospectionResultToSchemaTest and look at interfaceTypeDefinition variable, it cannot return a list of possible types ([Human, Droid]).

[github-actions]

Hello, this issue has been inactive for 60 days, so we're marking it as stale. If you would like to continue this discussion, please comment within the next 30 days or we'll close the issue.

[dondonz]

Hello as this issue is quite old and hasn't received any extra comments lately, I'll close this issue out.

If you'd like to make a new comment please do open a new issue, thanks!