Created Package Pipeline and updated docs

Created Package Pipeline entity for API
Updated the Package entity to support this
Updated the docs with deprecation notice
Removed BuildInfo entity

doc/api/packages.md

@@ -73,6 +73,10 @@ GET /groups/:id/packages
 curl --header "PRIVATE-TOKEN: <your_access_token>" https://gitlab.example.com/api/v4/groups/:id/packages?exclude_subgroups=true
 ```
 
+CAUTION: **Deprecation**
+> The `build_info` attribute in the response is deprecated in favour of `pipeline`.
+> Introduced [GitLab 12.10](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/28040).
+
 Example response:
 
 ```json
@@ -154,6 +158,10 @@ GET /projects/:id/packages/:package_id
 curl --header "PRIVATE-TOKEN: <your_access_token>" https://gitlab.example.com/api/v4/projects/:id/packages/:package_id
 ```
 
+CAUTION: **Deprecation**
+> The `build_info` attribute in the response is deprecated in favour of `pipeline`.
+> Introduced [GitLab 12.10](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/28040).
+
 Example response:
 
 ```json

ee/lib/ee/api/entities/package.rb

@@ -27,17 +27,17 @@ module EE
         expose :project_path, if: ->(obj, opts) { opts[:group] && Ability.allowed?(opts[:user], :read_project, obj.project) }
         expose :tags
 
-        PIPELINE_PROPS = [:created_at, :id, :sha, :ref, :status, :updated_at, :web_url, user: [:name, :avatar_url]].freeze
-
-        expose :pipeline, if: ->(obj) { obj.build_info } do |package|
-          ::API::Entities::Pipeline.represent package.build_info.pipeline, only: PIPELINE_PROPS
-        end
+        expose :pipeline, if: ->(package) { package.build_info }, using: Package::Pipeline
 
         private
 
         def project_path
           object.project.full_path
         end
+
+        def pipeline
+          object.build_info.pipeline
+        end
       end
     end
   end

ee/lib/ee/api/entities/package/build_info.rb → ee/lib/ee/api/entities/package/pipeline.rb

@@ -4,8 +4,8 @@ module EE
   module API
     module Entities
       class Package < Grape::Entity
-        class BuildInfo < Grape::Entity
-          expose :pipeline, using: ::API::Entities::PipelineBasic
+        class Pipeline < ::API::Entities::PipelineBasic
+          expose :user, using: ::API::Entities::UserBasic
         end
       end
     end