* added OpenID Connect as an SSO option

* minor fixes

* added comments, removed an option that shouldn't be set

* fixed Gemfile.lock

* added newline to end of Gemfile.lock

* removed tab from Gemfile.lock

* remove chomp

* codeclimate changes and small name change to make function's purpose clearer

* codeclimate fix

* added SSO buttons to /about page

* minor refactor

* minor style change

* removed spurious change

* removed unecessary conditional from ensure_valid_username and added support for auth.info.name in user_params_from_auth

* minor changes

* spelling: account

Signed-off-by: Josh Soref <jsoref@users.noreply.github.com>

* spelling: affiliated

Signed-off-by: Josh Soref <jsoref@users.noreply.github.com>

* spelling: appearance

Signed-off-by: Josh Soref <jsoref@users.noreply.github.com>

* spelling: autosuggest

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* spelling: cacheable

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* spelling: component

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* spelling: conversations

Signed-off-by: Josh Soref <jsoref@users.noreply.github.com>

* spelling: domain.example

Clarify what's distinct and use RFC friendly domain space.

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* spelling: environment

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* spelling: exceeds

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* spelling: functional

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* spelling: inefficiency

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* spelling: not

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* spelling: notifications

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* spelling: occurring

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* spelling: position

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* spelling: progress

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* spelling: promotable

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* spelling: reblogging

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* spelling: repetitive

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* spelling: resolve

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* spelling: saturated

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* spelling: similar

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* spelling: strategies

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* spelling: success

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* spelling: targeting

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* spelling: thumbnails

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* spelling: unauthorized

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* spelling: unsensitizes

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* spelling: validations

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* spelling: various

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Co-authored-by: Josh Soref <jsoref@users.noreply.github.com>

Fixes #15959

Introduced in #6540, OAUTH_REDIRECT_AT_SIGN_IN allowed skipping the log-in form
to instead redirect to the external OmniAuth login provider.

However, it did not prevent the log-in form on /about introduced by #10232 from
appearing, and completely broke with the introduction of #15228.

As I restoring that previous log-in flow without introducing a security
vulnerability may require extensive care and knowledge of how OmniAuth works,
this commit removes support for OAUTH_REDIRECT_AT_SIGN_IN instead for the time
being.

When using a CAS server, the users only have a temporary email
`change@me-foo-cas.com` which can't be changed but by an
administrator.

We need a new environment variable like for SAML to assume the email
from CAS is verified.

* config/initializers/omniauth.rb: define CAS option for assuming
  email are always verified.
* .env.nanobox: add new variable as an example.

The setting is not well documented by the provider, but allows for
clock skew between SP and IDP, see:
https://github.com/omniauth/omniauth-saml/blob/master/spec/omniauth/strategies/saml_spec.rb

Co-authored-by: kaiyou <dev@kaiyou.fr>

Otherwise, no matter what is given for CAS_VALIDATE_URL the default /serviceValidate path would be used.

* Code quality pass

* Typofix

* Update applications_controller_spec.rb

* Update applications_controller_spec.rb

* Cas authentication feature

* Config

* Remove class_eval + Omniauth initializer

* Codeclimate review

* Codeclimate review 2

* Codeclimate review 3

* Remove uid/email reconciliation

* SAML authentication

* Clean up code

* Improve login form

* Fix code style issues

* Add locales