introduction of server side rendering

[thescientist13]

Related Issue

resolves #708 (extracted from #812)

Summary of Changes

1. Introduce an ssr mode (ssr mode "conflicts" with MPA mode, see TODOs section below)
2. Add test cases
3. Added documentation

Opted for a Workers based approach for cache busting ESM in development

I think what's really cool about the possibilities here is how seamless it would be to run a hybrid application, such that you can have a set of static and dynamic pages and routes that can all share the same static resources, yet still feel like one app.

src/
  pages/
    about.md
    index.html
    contact.html
  routes/
    artists.js
    artist.js
  templates/
    app.html
    page.html
    product.html
  styles/
    theme.css
    artist.css
    main.css

In this way

• your landing / marketing "pages" can consist of static pages at build time (either as markdown or from a headless CMS)
• that can co-locate with "routes" that can be server rendered, but still re-use the same templating system

I tried to demonstrate that here in this PR with the "Artists" page, though obviously this will not work on Netlify, but you can try it locally!

1. Run yarn serve
2. Load localhost:8080/artists/

TODOs

1. ESM doesn't have the same caching mechanism features as CJS, including clearing the module cache, which means SSR routes don't reload on browser refresh.
   • Invalidate cache when using import nodejs/node#49442
   • Require cache equivalent in es modules nodejs/help#2806
2. Full support for
   • getTemplate()
   • getContent()
   • getMetadata()
3. Handle graph / frontmatter integration
4. Handle static asset bundling for serve command
5. Handle pre-rendering for serve command
6. Testing
7. Documentation
8. Fix windows github action error
9. Tracking / Questions / Car (all breaking changes would go into a release branch)
   1. (breaking) fluid "mode" / workspace configuration (autodetect based on pages, routes, etc) - have Greenwood auto detect project (mode) and expose client router option ("fluid" workspaces) #856
   2. (breaking) prerender: false by default and avoid puppeteer install - make prerender config option false by default #855
   3. (discussion) Fastify instead of Koa - Fastify Server and standard Request / Response #867
   4. Need more in memory driven architecture / pipelines which will become more handy as part of serverless, for things like Rollup bundling for SSR - Serverless (+ single route builds) #626 (comment)
   5. Need to have some sort of in cached bundling for SSR? Check if it exists on filesystem instead of in a Map for rollup bundling already bundled assets? - Serverless (+ single route builds) #626 (comment)
   6. why can't standard HTML just get all the data from the graph instead of all of this path finding stuff that was already done in the graph? - refactor html plugin serve to use graph to lookup files and content #854
   7. Review "meta" adjacent issues
      • Update documents per current status nodejs/modules#304
      • Proposal: Support loading package by own "name" nodejs/modules#306
      • title configuration should accept a (formatting) function as an option #655
10. Start release branch and follow same strategy as last release branch - with carry over TODOs
    • SSR guide (using AWS, Heoruku, etc)
    • More port options
    • website updates (now that we're more than just SSG)
    • static export option for SSR routes / pre-render off
    • TypeScript support for routes (post release?)
    • nested dynamic routes, e.g. /artist/${id} (post release?)
    • Graph lifecycle + standard plugin html refactoring (nice to have, else track)
11. Clean up demo code and merge into release branch , bring along any untracked items as new TODOs