Architecture content (#3156)

* WIP

* Early draft

* Getting closer, still needs more refinement

* Minor tweak

* More updates

* Added app topology examples

* Add note about eventual consistency

* Edit pass

* Fix link

* Apply suggestions from code review

Co-authored-by: Andy (Steve) De George <[email protected]>

* Address feedback

* Address feedback

* Fix up TOC

* TOC adjustment

* Clean up image

* Add upgrade content to welcome

* Adjust TOC

* TOC tweak

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Co-authored-by: Andy (Steve) De George <[email protected]>

Author: IEvangelist