Merge branch 'fix/ci-config-hidden-key-validation' into 'master'

Do not enforce using a hash with hidden ci key

## What does this MR do?

This MR remove the validation rule that was to strict.

## Why was this MR needed?

Enforcing hidden CI job configuration to be a hash, narrows options of using YAML anchors, and was not backwards compatbile.

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- Tests
  - [x] Added for this feature/bug
  - [ ] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

Closes #21512

See merge request !6079

2 files changed, 2 insertions, 3 deletions

diff --git a/lib/gitlab/ci/config/node/hidden_job.rb b/lib/gitlab/ci/config/node/hidden.rb
index 073044b66f8..fe4ee8a7fc6 100644
--- a/lib/gitlab/ci/config/node/hidden_job.rb
+++ b/lib/gitlab/ci/config/node/hidden.rb
@@ -5,11 +5,10 @@ module Gitlab
         ##
         # Entry that represents a hidden CI/CD job.
         #
-        class HiddenJob < Entry
+        class Hidden < Entry
           include Validatable
 
           validations do
-            validates :config, type: Hash
             validates :config, presence: true
           end
 
diff --git a/lib/gitlab/ci/config/node/jobs.rb b/lib/gitlab/ci/config/node/jobs.rb
index 51683c82ceb..a1a26d4fd8f 100644
--- a/lib/gitlab/ci/config/node/jobs.rb
+++ b/lib/gitlab/ci/config/node/jobs.rb
@@ -30,7 +30,7 @@ module Gitlab
 
           def compose!
             @config.each do |name, config|
-              node = hidden?(name) ? Node::HiddenJob : Node::Job
+              node = hidden?(name) ? Node::Hidden : Node::Job
 
               factory = Node::Factory.new(node)
                 .value(config || {})