How to catch outgoing request

I have a peculiar situation.
I am sending mutation to 3rd party graphQL endpoint and it works great if I do it from Hasura console or from some playground, but when I do it from our server with apollo it breaks somethings.

The gql and the parameters are the same, so it is probably some additional stuff is at fault.
Thus I want to check final request with all the cookies, headers and stuff - exactly as received by 3rd party graphQL endpoint.
Is there a way to do that?

I have used middelware like the one described here Advanced HTTP networking - Client (React) - Apollo GraphQL Docs (with plain console.log instead of changing headers).
There are two cases. If I add middleware before link, I get following info in operation

  variables: {
    option_ref_id: 'FAKE_OPTION_REF_ID',
    payment_card_obj: {
      holder: [Object],
      number: '4916230747828208',
      CVC: '123',
      expire: [Object]
  extensions: {},
  operationName: 'bookQuote',
  query: {
    kind: 'Document',
    definitions: [ [Object] ],
    loc: { start: 0, end: 2737 }

which is nice, but not enouph.

If I add middleware after link, I get an error

Error: You are calling concat on a terminating link, which will have no effect
    at new LinkError 
    at ApolloLink.concat 
    at createApolloClient (webpack-internal:///./lib/apolloClient.js:120:65)
    at eval (webpack-internal:///./models/users.js:55:80)
  link: HttpLink {
    request: [Function (anonymous)],
    options: {
      uri: '',
      credentials: 'same-origin',
      headers: [Object],
      fetch: [Function]

I think both those results in combination may allow me to find out what is the problem, but I would like to know - does not apollo add some of his own headers (cache headers or something like ‘hey I’m apollo’)?