fix(federation): override federated resolveType for interfaces

[thomas-advantitge]

PR Checklist

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• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Other... Please describe:

What is the current behavior?

Interfaces example (https://docs.nestjs.com/graphql/interfaces) with resolveType doesn't work when changing GraphQLModule to GraphQLFederationModule.

{
  "errors": [
    {
      "message": "Abstract type \"Party\" must resolve to an Object type at runtime for field \"Query.parties\". Either the \"Party\" type should provide a \"resolveType\" function or each possible type should provide an \"isTypeOf\" function.",
      "locations": [
        {
          "line": 2,
          "column": 3
        }
      ],
...

Issue Number: N/A

What is the new behavior?

Resolve type function is executed when using GraphQLFederationModule.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

// lib/federation/graphql-federation.factory.ts

// autoGeneratedSchema is including types with resolveType function
const autoGeneratedSchema: GraphQLSchema = await this.gqlSchemaBuilder.buildFederatedSchema(
  options.autoSchemaFile,
  options,
  this.resolversExplorerService.getAllCtors(),
);
// executableSchema "erases" this field
let executableSchema: GraphQLSchema = buildFederatedSchema({
  typeDefs: gql(printSchema(autoGeneratedSchema)),
  resolvers: this.getResolvers(options.resolvers),
});

[kamilmysliwiec]

Would you be able to add an e2e test for this issue (or update one of the existing tests) so we can make sure we never break this behavior in the future?

[thomas-advantitge]

@kamilmysliwiec as we encountered a related problem concerning the absence of field directives on interfaces, added the fix in this PR as well, extending the new e2e test.

[kamilmysliwiec]

LGTM