Merge branch 'feature/send-registry-address-with-build-payload' into 'master'

Send registry address with build payload

## What does this MR do?

Adds `registry_url` as a part of a build payload, when sending a response to a GitLab Runner which requested a new build.

## Are there points in the code the reviewer needs to double check?

Change in `lib/ci/api/entities.rb`.

## Why was this MR needed?

This is one of the steps needed to add support for private/protected registries hosted with GitLab CE/EE.

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [x] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [x] API support added
- Tests
  - [x] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] 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 it does - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

Related to gitlab-org/gitlab-ci-multi-runner#1828, gitlab-org/gitlab-ci-multi-runner!386, gitlab-org/gitlab-ci-multi-runner#1434

See merge request !7474

4 files changed, 70 insertions, 0 deletions

diff --git a/lib/ci/api/entities.rb b/lib/ci/api/entities.rb
index 66c05773b68..792ff628b09 100644
--- a/lib/ci/api/entities.rb
+++ b/lib/ci/api/entities.rb
@@ -32,6 +32,10 @@ module Ci
         expose :artifacts_file, using: ArtifactFile, if: ->(build, _) { build.artifacts? }
       end
 
+      class BuildCredentials < Grape::Entity
+        expose :type, :url, :username, :password
+      end
+
       class BuildDetails < Build
         expose :commands
         expose :repo_url
@@ -50,6 +54,8 @@ module Ci
 
         expose :variables
         expose :depends_on_builds, using: Build
+
+        expose :credentials, using: BuildCredentials
       end
 
       class Runner < Grape::Entity
diff --git a/lib/gitlab/ci/build/credentials/base.rb b/lib/gitlab/ci/build/credentials/base.rb
new file mode 100644
index 00000000000..29a7a27c963
--- /dev/null
+++ b/lib/gitlab/ci/build/credentials/base.rb
@@ -0,0 +1,13 @@
+module Gitlab
+  module Ci
+    module Build
+      module Credentials
+        class Base
+          def type
+            self.class.name.demodulize.underscore
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/ci/build/credentials/factory.rb b/lib/gitlab/ci/build/credentials/factory.rb
new file mode 100644
index 00000000000..2423aa8857d
--- /dev/null
+++ b/lib/gitlab/ci/build/credentials/factory.rb
@@ -0,0 +1,27 @@
+module Gitlab
+  module Ci
+    module Build
+      module Credentials
+        class Factory
+          def initialize(build)
+            @build = build
+          end
+
+          def create!
+            credentials.select(&:valid?)
+          end
+
+          private
+
+          def credentials
+            providers.map { |provider| provider.new(@build) }
+          end
+
+          def providers
+            [Registry]
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/ci/build/credentials/registry.rb b/lib/gitlab/ci/build/credentials/registry.rb
new file mode 100644
index 00000000000..55eafcaed10
--- /dev/null
+++ b/lib/gitlab/ci/build/credentials/registry.rb
@@ -0,0 +1,24 @@
+module Gitlab
+  module Ci
+    module Build
+      module Credentials
+        class Registry < Base
+          attr_reader :username, :password
+
+          def initialize(build)
+            @username = 'gitlab-ci-token'
+            @password = build.token
+          end
+
+          def url
+            Gitlab.config.registry.host_port
+          end
+
+          def valid?
+            Gitlab.config.registry.enabled
+          end
+        end
+      end
+    end
+  end
+end