[RF-DOCS] Sign up guide (rails#55254)

* First draft of the sign up guide

* Add email confirmations controller test and other small tweaks

* Assert flashes and update generated User mailer test

* Add one final full test suite run

* Apply suggestions from code review

Co-authored-by: Amanda Perino <[email protected]>

* Rename sign_up.md to sign_up_and_settings.md

* Apply suggestions from code review

Co-authored-by: Amanda Perino <[email protected]>

* Tweak copy

* Explain requiring only unauthenticated access for sign up

* Tweak what's next

* Apply suggestions from code review

Co-authored-by: Amanda Perino <[email protected]>

* Apply suggestions from code review

* Apply suggestions from code review

* Update guides/source/sign_up_and_settings.md

* Apply suggestions from code review

Co-authored-by: Hartley McGuire <[email protected]>
Co-authored-by: Matheus Richard <[email protected]>

* Update guides/source/sign_up_and_settings.md

Co-authored-by: Kyoungwon Lee (Stark) <[email protected]>

* Update guides/source/sign_up_and_settings.md

Co-authored-by: Jeremy BERTRAND <[email protected]>

* Update guides/source/sign_up_and_settings.md

* Apply suggestion from @excid3

* Apply suggestion from @excid3

* Add tip for additional validations for password security

* Add tip to explain current attributes

* Add view changes to sign up guide for admin area

* Add return to all tutorials link

* Add relative translation after moving products index

* Fix tests

* Reformat to 80 char line width

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Co-authored-by: Amanda Perino <[email protected]>
Co-authored-by: Hartley McGuire <[email protected]>
Co-authored-by: Matheus Richard <[email protected]>
Co-authored-by: Kyoungwon Lee (Stark) <[email protected]>
Co-authored-by: Jeremy BERTRAND <[email protected]>

Author: 6 people