Segregate interface require to make CI/CD entity processable

This commit segregates interface that is require to make CI/CD entity
processable, like `Ci::Build`. With this change it is not clear and
explicit what methods need to be implement to pass an object to pipeline
processing service.

app/models/ci/build.rb

@@ -3,6 +3,7 @@
 module Ci
   class Build < CommitStatus
     prepend ArtifactMigratable
+    include Ci::Processable
     include TokenAuthenticatable
     include AfterCommitQueue
     include ObjectStorage::BackgroundMove

app/models/ci/pipeline.rb

@@ -25,6 +25,8 @@ module Ci
 
     has_many :stages, -> { order(position: :asc) }, inverse_of: :pipeline
     has_many :statuses, class_name: 'CommitStatus', foreign_key: :commit_id, inverse_of: :pipeline
+    has_many :processables, -> { where(type: %w[Ci::Build Ci::Bridge]) },
+             class_name: 'CommitStatus', foreign_key: :commit_id, inverse_of: :pipeline
     has_many :builds, foreign_key: :commit_id, inverse_of: :pipeline
     has_many :trigger_requests, dependent: :destroy, foreign_key: :commit_id # rubocop:disable Cop/ActiveRecordDependent
     has_many :variables, class_name: 'Ci::PipelineVariable'

app/models/concerns/ci/processable.rb

+# frozen_string_literal: true
+
+module Ci
+  ##
+  # This module implements methods that need to be implemented by CI/CD
+  # entities that are supposed to go through pipeline processing
+  # services.
+  #
+  #
+  module Processable
+    def schedulable?
+      raise NotImplementedError
+    end
+
+    def action?
+      raise NotImplementedError
+    end
+
+    def artifacts?
+      raise NotImplementedError
+    end
+
+    def expanded_environment_name
+      raise NotImplementedError
+    end
+  end
+end

app/services/ci/process_pipeline_service.rb

@@ -55,7 +55,7 @@ module Ci
     # rubocop: enable CodeReuse/ActiveRecord
 
     def created_builds
-      pipeline.builds.created
+      pipeline.processables.created
     end
 
     # This method is for compatibility and data consistency and should be removed with 9.3 version of GitLab