SSR implementation plan

[bigopon]

There are a few features to implement before we can deliver SSR:

1. The abiility to render an application in the server to a html, and:

• the ability to have dom like environment for template to render, like HTMLElement but lighter weight and just need to be enough to support this rendering mode

2. The ability to hydrate an existing dom structure based on a given custom element/ view (from template controller) definition. This is different with enhance:

• enhance takes an existing element as the template
• hydrate reuses an existing element as the output of the rendering process and apply correct instruction to different elements within this dom structure.
  This is the most challenging part since there' a few ways instructions and DOM can be merged: custom element, slot, portal, au-compose, router at the moment.
  This'll need to work with the server side rendered html above