Improve `composeClient.executeQuery` validation error format

When the executeQuery function is called with a data validation error, it’s hard to parse and show some feedback to the user.

Currently the message returned is "HTTP request to 'http://localhost:7007/api/v0/streams' failed with status 'Internal Server Error': {\"error\":\"Validation Error: data/title must NOT have fewer than 10 characters\"}".

This code:

const data = await composeClient.executeQuery(`...`);
console.log(data);

Produces:

{
    "errors": [
        {
            "message": "HTTP request to 'http://localhost:7007/api/v0/streams' failed with status 'Internal Server Error': {\"error\":\"Validation Error: data/title must NOT have fewer than 10 characters\"}",
            "locations": [
                {
                    "line": 3,
                    "column": 9
                }
            ],
            "path": [
                "createPost"
            ]
        }
    ],
    "data": {
        "createPost": null
    }
}

Just returning the JSON or other would make it easier to catch and provide some context to the user on what went wrong.