Assert response headers

[m0d7]

RestAssured.Net/src/RA/ResponseContext.cs

Lines 72 to 82 in 764c883

	/// <summary>
	/// Setup a test against the response headers.
	/// </summary>
	/// <param name="ruleName"></param>
	/// <param name="key"></param>
	/// <param name="func"></param>
	/// <returns></returns>
	public ResponseContext TestHeader(string ruleName, string key, Func<string, bool> func)
	{
	return TestWrapper(ruleName, () => func.Invoke(HeaderValue(key.Trim())));
	}

TestHeader method states that Setup a test against response headers., however, the assert is not being done against Response.Headers, but Response.Content.Headers:

RestAssured.Net/src/RA/ExecutionContext.cs

Lines 293 to 306 in 764c883

	private ResponseContext BuildFromResponse(HttpResponseMessageWrapper result)
	{
	// var content = AsyncContext.Run(async () => await result.Response.Content.ReadAsStringAsync());
	var content = result.Response.Content.ReadAsStringAsync().GetAwaiter().GetResult();
	return new ResponseContext(
	result.Response.StatusCode,
	content,
	result.Response.Content.Headers.ToDictionary(x => x.Key.Trim(), x => x.Value),
	result.ElaspedExecution,
	_loadReponses.ToList()
	);
	}

As far as I know, currently there is no possibility to assert Response.Headers. So this PR fixes this issue.