How to pass token from Postman to Graphql Mesh

Question

I am trying to build a unified gateway for my over 50 different graphql endpoints that I want to have them accessed over one gateway and I have choosen to use graphqlmesh. I am bit lost, I can hard code the token, on the mesh configuration but that won't work on a production bases as I would need to pass the generated token to the app,

Currently I can do this

sources:
  - name: rick-and-morty
    handler:
      graphql:
        endpoint: https://rickandmortyapi.com/graphql

  - name: trevorblades
    handler:
      graphql:
        endpoint: https://countries.trevorblades.com

  - name: bff
    handler:
      graphql:
        endpoint: https://teller.com/svc/bff/graphql
        source: ./sdl.gql
        operationHeaders:
          Authorization: Bearer rhuirijjsihjbfejnbsd,ojfjerbfbjihjbefnfnjhiuureiwbanbk
      transforms:
        - encapsulate:
            name: bff
            applyTo:
              query: true
              mutation: true
              subscription: true

How can I set this bit

operationHeaders:
              Authorization: Bearer rhuirijjsihjbfejnbsd,ojfjerbfbjihjbefnfnjhiuureiwbanbk

to pick the token from postman,

I have tried this

- name: bff
    handler:
      graphql:
        endpoint: https://teller.com/svc/bff/graphql
        source: ./sdl.gql
        operationHeaders:
          Authorization: Bearer {context.headers['x-my-api-token']}
      transforms:
        - encapsulate:
            name: bff
            applyTo:
              query: true
              mutation: true
              subscription: true

But the app doesn't come up it ends up throwing an error

AggregateError: Failed on fetching Federated SDL for bff at /Users//WebstormPuserrojects/Kyosk-GraphQL-Gateway/node_modules/@graphql-mesh/merger-stitching/cjs/index.js:49:27 at processTicksAndRejections (node:internal/process/task_queues:96:5) at async Object.getWithSet (/Users/user/WebstormProjects/GraphQL-Gateway/node_modules/@graphql-mesh/store/cjs/index.js:167:38) at async StitchingMerger.replaceFederationSDLWithStitchingSDL (/Users/user/WebstormProjects/GraphQL-Gateway/node_modules/@graphql-mesh/merger-stitching/cjs/index.js:35:25)

how can I set my mesh gateway to accept the bearer token from the clients like postman