Fix indices.get_alias error response

[pquentin]

Our recordings show two different errors paths. The first one is supported:

{
  "api": "indices.get_alias",
  "file": "/test/free/indices.get_alias/10_basic.yml",
  "name": "Getting alias on an non-existent index should return 404",
  "origin": "yaml",
  "request": {
    "args": {
      "index": "non-existent",
      "name": "foo"
    }
  },
  "response": {
    "headers": {
      "content-encoding": "gzip",
      "content-length": "164",
      "content-type": "application/json",
      "x-elastic-product": "Elasticsearch"
    },
    "payload": {
      "error": {
        "index": "non-existent",
        "index_uuid": "_na_",
        "reason": "no such index [non-existent]",
        "resource.id": "non-existent",
        "resource.type": "index_or_alias",
        "root_cause": [
          {
            "index": "non-existent",
            "index_uuid": "_na_",
            "reason": "no such index [non-existent]",
            "resource.id": "non-existent",
            "resource.type": "index_or_alias",
            "type": "index_not_found_exception"
          }
        ],
        "type": "index_not_found_exception"
      },
      "status": 404
    },
    "statusCode": 404
  }
}

But the second one was not supported:

{
  "api": "indices.get_alias",
  "file": "/test/free/indices.delete_alias/all_path_options.yml",
  "name": "check delete with * index",
  "origin": "yaml",
  "request": {
    "args": {
      "name": "alias1"
    }
  },
  "response": {
    "headers": {
      "content-encoding": "gzip",
      "content-length": "70",
      "content-type": "application/json",
      "x-elastic-product": "Elasticsearch"
    },
    "payload": {
      "error": "alias [alias1] missing",
      "status": 404
    },
    "statusCode": 404
  }
}

Not sure if changing ErrorResponseBase this way is OK or not.

[github-actions]

Following you can find the validation results for the API you have changed.

API	Status	Request	Response
indices.get_alias	🟢	86/86	86/86

You can validate this API yourself by using the make validate target.

[l-trotta]

this is probably breaking for all static clients generator since it's a new union

[flobernd]

Does this only apply to indices.get_alias?

[pquentin]

Too bad. Can you think of a non breaking way to fix this? The common case is actually the second one, but of course less common than the happy path

[pquentin]

@flobernd Sesrching the docs did turn up a few cases, but it seems pretty non standard.

[l-trotta]

@pquentin let's bring this up in the next meeting, it's should be easy to map this, but we all have to be aware of the change

[pquentin]

Closing as we'll be skipping this test instead.