Add WebGraphQlRequest constructor

[nkonev]

With direct passing query, operationName, variables. It will help to create multipart GraphQlHttpHandler

It is small part of #430 which will help to create multipart GraphQlHttpHandler

[rstoyanchev]

Given the existing constructor takes a Map, couldn't you do this over here:

Map<String, Object> body = Map.of(
		"query", query, "operationName", opName, "variables", queryVariables, "extensions", extensions);

WebGraphQlRequest graphQlRequest = new WebGraphQlRequest(
		serverRequest.uri(), serverRequest.headers().asHttpHeaders(),
		body,
		serverRequest.exchange().getRequest().getId(),
		serverRequest.exchange().getLocaleContext().getLocale());

Or otherwise the existing constructor becomes a simple delegation to the new one, but looking at the above I'm not sure it really helps that much.

[nkonev]

Yes, thank you, it looks workable

        Map<String, Object> body = Map.of(
                "query", query, "operationName", StringUtils.hasText(opName) ? opName : "", "variables", queryVariables, "extensions", extensions);

        WebGraphQlRequest graphQlRequest = new WebGraphQlRequest(
			serverRequest.uri(), serverRequest.headers().asHttpHeaders(), body,
			this.idGenerator.generateId().toString(), LocaleContextHolder.getLocale());