fix: federation schema builder

[endroca]

Referer: #1780

## PR Checklist
Please check if your PR fulfills the following requirements:

• 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?

• 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?

Issue Number: #1597

What is the new behavior?

The generated schema contains also the directives needed for the federation.

Does this PR introduce a breaking change?

• Yes
• No

Other information

[Andrius0124]

@kamilmysliwiec
Thanks for the great framework!
Anyway we could speed up this PR?
It's a blocker for us.

[endroca]

@kamilmysliwiec Thanks for the great framework! Anyway we could speed up this PR? It's a blocker for us.

@Andrius0124 A temporary solution that i am using in my projects

      transformSchema: (schema) => {
        writeFileSync(
          join(process.cwd(), 'src/schema.gql'),
          printSubgraphSchema(schema),
        );
        return schema;
      },

I hope it helps

[Andrius0124]

@endroca Huge help! Works like a charm! Thanks

[Francismb]

Looking forward to it!

[mandajoan]

Hello! Ran into this issue and journeyed along the various issues reported to end up on this PR. Any updates on the status of this getting merged or input on new solutions w/the more recent package updates?

[renanpupin]

I can confirm this is still a problem.

[jasonmacdonald]

This is a 3 year old issue that has a simple fix and yet still isn't addressed. This completely breaks using Nest with code-first and federation 2. I'm so confused about how this is just lingering.