* Add deprecation warning to old integration
* Add user docs
* Add admin docs

- Move steps to new doc
- Move all concepts to different docs

Many code blocks are 4spaced, and they render in GitLab
without coloring as a result, even though they are
fenced with a language label. If in a list, other items
will render as being in a code block too, even if not
meant to. This fixes all these issues for many admin
docs (part 2)