make ISpaPrerenderer.RenderToString and aspnet-prerendering createServerRenderer to generic

[petvas]

Is your feature request related to a problem? Please describe.

Microsoft.AspNetCore.SpaServices.Prerendering.RenderToStringResult has one Globals in it, it works ok with an example application but in real life I ended up overloading it.
Example:
Basic react app with ssr:

• react
• Redux
• React Router
• styled-components
• React Helmet
• @loadable

server side entry point looks like this:

const helmetData = Helmet.renderStatic();
        const helmet = {
            baseString: helmetData.base.toString(),
            bodyAttributes: helmetData.bodyAttributes.toString(),
            htmlAttributes: helmetData.htmlAttributes.toString(),
            link: helmetData.link.toString(),
            meta: helmetData.meta.toString(),
            noscript: helmetData.noscript.toString(), // :D
            script: helmetData.script.toString(),
            style: helmetData.style.toString(),
            title: helmetData.title.toString(),
        };


resolve({
            html: result,
            globals: {
                scriptTags,
                linkTags,
                styleTags,
                helmet,
                PreloadedState,
            }
        });

AspNetCore looks like this:

 public class HelmetData {
        public string baseString;
        public string bodyAttributes;
        public string htmlAttributes;
        public string link;
        public string meta;
        public string noscript;
        public string script;
        public string style;
        public string title;
    }
    public class SSRExtraParams
    {
        public string scriptTags;
        public string linkTags;
        public string styleTags;
        public HelmetData helmet;
        public JObject PreloadedState;
    }

           var result = await prerenderer.RenderToString("ssrroot/dist/ssr", null, new { test = "test"  });
            
            ViewData["PrerenderedHtml"] = result.Html;

            var extraParams = result.Globals.ToObject<SSRExtraParams>();

            ViewData["scriptTags"] = extraParams.scriptTags;
            ViewData["linkTags"] = extraParams.linkTags;
            ViewData["styleTags"] = extraParams.styleTags;
            ViewData["helmet"] = extraParams.helmet;
            ViewData["PreloadedState"] = extraParams.PreloadedState;

Describe the solution you'd like

I would like to make RenderToString generic on server side:

var result = await prerenderer.RenderToString<MyCustomRenderToStringResult>(/*...*/);

and aspnet-prerendering createServerRenderer generic on client side:

createServerRenderer<MyCustomRenderResult>((params) => {/*...*/})

Additional context

It just feels using global like this is not right, it would be more elegant end flexible if we can set the return type so its suits better with everyone needs.

[mkArtakMSFT]

We're closing this issue as this doesn't align with our long-term plans in this area. You can read more details about our vision for this area at #12890.