Support Query/Mutation filtering

[nabeix]

Problem

We need generate documents for multiple client from one schema.
GraphQL documents generates documents of all Query/Mutation.
So, the generated documents includes unnecessary document for a client.
It makes overhead of module size.

Suggestion

codegen.yml

overwrite: true
schema:
  - ./schemas/**/*.graphql

generates:
  ./documents/index.graphql:
    plugins:
      - graphql-codegen-documents
    config:
      - tags:
          - client

index.graphql

type Query {
  books(first: Int!, offset: Int!): BooksConnection!  # graphql-codegen-documents: tag=client

  user(first: Int!, offset: Int!): UserConnection! # this is always target
}

I don't know graphql codegen plugin can read # comment line.

[nabeix]

Directive is better than comment.
https://www.graphql-tools.com/docs/schema-directives/