Add hints for Kerberos sign-in failure

We do not know what went wrong when this page is shown but we can guess.

See merge request !583

Use RequestStore to cache the contents of the current License

Fixes #695 

See merge request !566

Merge branch '799-viewing-a-mr-with-approvals-with-an-anonymous-user-results-in-error-500' into 'master'

Don't check if anonymous user can update MR

Closes #799. Interestingly, I think previously we showed the 'Approve MR' button to anonymous users when an MR had approvals from anyone allowed, but we didn't blow up with a 500 error.

See merge request !582

Document how to upgrade from password-based Kerberos



See merge request !575

Display the JSON payload in settings page for EE usage ping

Screenshot:

![image](/uploads/4d6379a73cc66f03000f8aebd31c8355/image.png)


See merge request !580

Licenses are already being destroyed by the `before(:all)` hook,
removing them from a `before(:each)` hook breaks feature specs when we
have multiple `context` blocks.

See: https://gitlab.com/gitlab-org/gitlab-ee/blob/ff9ad690650c23665439499d23f3ed22103b55bb/spec/spec_helper.rb#L50

Performance improvement of push rules

We don't need to check temp ref anymore since  https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/563 is merged

related https://gitlab.com/gitlab-org/gitlab-ce/issues/14280#note_13198239

See merge request !578

[Elastic] Suppress ActiveRecord::RecordNotFound error in ElasticIndexWorker

Fixes https://gitlab.com/gitlab-com/infrastructure/issues/233

See merge request !577

Fix Gemfile.lock

It has been committed during CE->EE merge. Sorry

See merge request !576

Mention Kerberos in CHANGELOG-EE

This was forgotten in https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/548

See merge request !574

Fix bad Group class resolution when querying LDAP via API

When querying LDAP groups via the API, there was a 500 error with a strange stack. Thanks to @DouweM we figured out that in the context of the API, it's choosing `::Group` instead of `EE::Gitlab::LDAP::Group`. This makes it just specific enough to work. 

See merge request !572

Improve error text for LDAP group links

See merge request !573

Add ticket-based Kerberos sign-ins

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/745

This is meant as a replacement for omniauth-kerberos. This MR does not rip out or disable omniauth-kerberos, however, because that has the risk of locking out all Kerberos users on Kerberos-enabled GitLab server that does not have a service keytab yet.

On GitLab installations that have a keytab, namely those which have 'git access via SPNEGO' enabled, this change will automatically enable ticket-based sign-ins. 

See merge request !548

Fix autoloading issue in test environment

Always prefer to use the full class namespace when specifying a superclass inside a module, because autoloading can occur in a different order between execution environments.

```ruby
module Foo
  class Base
    def initialize
      raise "This is the wrong super class!"
    end
  end
end

module Foo
  module Bar
    class Sample < Base
      # Inherits from ::Foo::Base because Foo::Bar::Base isn't defined yet
    end
  end
end

module Foo
  module Bar
    class Base
      def initialize
        puts "Success!"
      end
    end
  end
end

> Foo::Bar::Sample.new
=> RuntimeError: This is the wrong super class!
```

The trouble occurs when Rails has already autoloaded `Gitlab::SearchResults` and not `Gitlab::Elastic::SearchResults`. In this case, Rails will never need to autoload `Gitlab::Elastic::SearchResults` because `Gitlab::SearchResults` already matches the superclass. This is why this [build](https://gitlab.com/gitlab-org/gitlab-ee/builds/2464466) only fails when the spec run after `spec/lib/gitlab/search_results_spec.rb`.

/cc @DouweM @rspeicher @vsizov 



See merge request !571

Always prefer to use the full class namespace when specifying a
superclass inside a module, because autoloading can occur in a
different order between execution environments.

Uninitialized constant ElasticIndexerWorker::Client

Fixes https://gitlab.com/gitlab-org/gitlab-ee/issues/772

See merge request !554

CE upstream



See merge request !570

CE upstream

@timothyandrew Please resolve:

```
spec/lib/gitlab/git_access_spec.rb
lib/gitlab/checks/change_access.rb
lib/gitlab/git_access.rb
lib/gitlab/git_access_wiki.rb
```

See merge request !568

Use value of `yaml_variables` and `when` from config_processor if undefined

## What does this MR do?
Uses `yaml_variables` and `when` from config_processor if values for these are undefined.

## Why was this MR needed?
Old builds doesn't have this columns initialised. 
Thus makes the retries on these builds to not work properly.
This is regression introduced by https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5296.

## Does this MR meet the acceptance criteria?

- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)


See merge request !5342

Added redirect_to_referer to login link on issues

## What does this MR do?

Adds a `redirect_to_referer` param to login & register links on issues when not logged in. This makes the login box redirect back to the issue after login.

## What are the relevant issue numbers?

Closes #19968 

See merge request !5344