Improve error handling of allProjectsByFunction

[IvanIvanoff]

Changes

Properly propagate the error when the watchlist from the JSON arguments is not existing.

query($fn:json){
    allProjectsByFunction(function: $fn) {
      projects {
        slug name ticker
    }
  }
}

{
  "fn": "{\"name\":\"selector\",\"args\":{\"baseProjects\":[{\"watchlistId\":5496}],\"filters\":[],\"orderBy\":{\"aggregation\":\"avg\",\"dynamicFrom\":\"7d\",\"direction\":\"desc\",\"dynamicTo\":\"now\",\"metric\":\"dev_activity_1d\"},\"pagination\":{\"page\":1,\"pageSize\":10}}}"
}

Old response:

{
  "errors": {
    "details": "Internal server error"
  }
}

New response:

{
  "data": {
    "allProjectsByFunction": null
  },
  "errors": [
    {
      "message": "Watchlist with id 5496 does not exist",
      "path": [
        "allProjectsByFunction"
      ],
      "locations": [
        {
          "line": 2,
          "column": 5
        }
      ]
    }
  ]
}

Ticket

Checklist:

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have tried to find clearer solution before commenting hard-to-understand parts of code
• I have added tests that prove my fix is effective or that my feature works