This is a step for #29118.

Add a single metric to count successful logins.

Summary types are not supported so remove Collector.  Either
we need to support the summary type or we need to create a
multiprocess-friendly Collector.

Add config to load prometheus and set up the Collector and the
Exporter.

Fix `Gemfile` as current prometheus-client gemspec is missing the
`mmap2` dependency.

It uses a user activity table instead of a column in users.
Tested with mySQL and postgreSQL

 - cleanup formating in haml
 - clarify time window is in seconds
 - cleanup straneous chunks in db/schema
 - rename count_uniqe_ips to update_and_return_ips_count
 - other

This reverts commit cb10b725c8929b8b4460f89c9d96c773af39ba6b.

test: replaced signed_out message check with check for sign_in button

fixes #25294

After this change the sign-in-success flash message will not be shown

refactor: set flash message to be nil while signing in

test: changed tests to reflect removal of sign-in message

refactor: adding signed_in message back

See Merge Request !7837

issue#24982

The helper constructs the path for a given oauth provider since Devise 4.0 deprecated passing the provider to the omniauth authentication path.

Fixes #18110.

This reverts commit 13e37a3e.

- "two-factor" for OTP-based 2FA
- "two-factor-via-u2f-device" for U2F-based 2FA
- "standard" for non-2FA login

- Move the `authenticate_with_two_factor` method from
  `ApplicationController` to the `AuthenticatesWithTwoFactor` module,
  where it should be.

Closes #17765

This reverts commit 3e991230.

# Conflicts:
#	app/models/project.rb

Prior, if a user had 2FA enabled and checked the "Remember me" field,
the setting was ignored because the OTP input was on a new form and the
value was never passed.

Closes #18000

This commit attempts to change default user search scope if otp_user_id
session variable has been set. If it is present, it means that user has
2FA enabled, and has already been verified with login and password. In
this case we should look for user with otp_user_id first, before picking
it up by login.

Closes #1980

Addresses internal https://dev.gitlab.org/gitlab/gitlabhq/issues/2605

See https://github.com/tinfoil/devise-two-factor/pull/43

Logic for redirect path moved to a filter.

Add an option to automatically sign-in with an Omniauth provider without showing the GitLab sign-in page

This is useful when integrating with existing SSO environments and we want to use a single Omniauth provider for
all user authentication.

This makes it consistent with the Invalid email/password error message
from the previous step.

Also adds test case for providing an invalid 2FA code and then a valid
one without re-entering username and password.