Fix file name discrepancies and bring attention to server null data no errors issue in Kotlin Tutorial

[YuanRuQian]

Hi, I mentioned these issues in my Discord post

Changes Made:

• Fixed a typo in the "Add More Info" section where it incorrectly mentioned "LaunchListAdapter.kt" instead of "LaunchList.kt" for binding GraphQL data.
• Addressed a mention in the "Subscriptions" section regarding error handling location in the client code. The mentioned location (MainActivity.kt) didn't match the actual code (Apollo.kt).

Additionally, In the "Add a Details View" section , I observed a discrepancy in the behavior of the current server demo when handling invalid IDs. According to the expected behavior, the server should return errors when provided with invalid IDs. However, upon testing by providing invalid IDs in the query, all responses contained only null data but no errors. Maybe the dev team to investigate this issue to ensure new learners encounter the expected behavior.

Query:

query LaunchDetails($id: ID!) {
  launch(id: $id) {
    id
    site
    mission {
      name
      missionPatch(size: LARGE)
    }
    rocket {
      name
      type
    }
    isBooked
  }
}

Query Variables:

{
  "id": "invalidId"
}

Expected response:

{
  "errors": [
    {
      "message": "Cannot read property 'flight_number' of undefined",
      "locations": [
        {
          "line": 1,
          "column": 32
        }
      ],
      "path": [
        "launch"
      ],
      "extensions": {
        "code": "INTERNAL_SERVER_ERROR"
      }
    }
  ],
  "data": {
    "launch": null
  }
}

Actual response:

Thank you!

[apollo-cla]

@YuanRuQian: Thank you for submitting a pull request! Before we can merge it, you'll need to sign the Apollo Contributor License Agreement here: https://contribute.apollographql.com/

[martinbonnin]

Thanks a lot for catching those ❤️

You're also 100% right on the behaviour change about errors vs null. Nullability in GraphQL is one of my favorite topics, I'll investigate this with the team and report here

[BoD]

👍

[martinbonnin]

(keeping this open for now as a reminder that we still need to investigate the tutorial issue).

I'll merge and open a separate tutorial issue at the end of the week if we haven't figured it out before that!

[martinbonnin]

Fixing the tutorial might take a bit of time. Merging this as-is as opened #5747 as a follow up. Thanks again 🙏