* Edit Security section for clarity.
The edit includes:
* Rewrite of every passive voice instance.
* Consistent use markup to reference code from the examples in the text.
* Added emphasis to make key concepts clearer.
* Added links to the Identity section of the docs.
* Update authentication concept doc.
* Fix lint errors.
* Address comments and fixed some links.
* Remove feature stages change from this PR.
I will make a separate PR for it.
* Consolidate the security concept pages into a single page.
- This updates the security concept material to be on a single page, which matches the
change done last week for the rest of the concept material. This ends up being a less clicky
more directed introduction for newcomers to the platform.
- While I was there, I moved the redundant What is Istio page from our about section and stuck
the content at the top of the What is Istio page in the Concepts section.
Rigs Caballero
Martin Taillefer
Stefan Büringer
Limin Wang
Yangmin