Documentation topic: Authentication

See the general Documentation guidelines http://docs.gitlab.com/ce/development/doc_styleguide.html

What does this MR do?

Add a new topic to https://docs.gitlab.com/ce/topics/ = Authentication

Where: https://docs.gitlab.com/ce/topics/authentication/

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/30744

cc/ @axil FYI

@SeanPackham would you please review/merge?

mentioned in merge request !10299 (closed)

added 1 commit

• 0b3da49e - fix links

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resolved all discussions

added 2 commits

• f7cafe1d - fix typo
• 85cfde83 - typo

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added 52 commits

• 85cfde83...069c54a7 - 51 commits from branch master
• 40991fc3 - fix conflict

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@SeanPackham as you had already approved this in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10299#note_26724133, I'll merge it

assigned to @marcia

changed milestone to %9.1

merged

mentioned in commit a62ae94d

added ~149423 ~17488 labels

mentioned in merge request !10643 (merged)

Picked into 9-1-stable, will go into 9.1.0-rc2

mentioned in commit d0659153

mentioned in merge request !11045 (merged)