Rename user_id to author_id for Versions

https://gitlab.com/gitlab-org/gitlab/merge_requests/17316 introduced
the user_id column, however, after beginning to use it, it appears as
though "author" is the more frequently used association name for the
user who has created some data in GitLab.

db/migrate/20191014025629_rename_design_management_version_user_to_author.rb

+# frozen_string_literal: true
+
+class RenameDesignManagementVersionUserToAuthor < ActiveRecord::Migration[5.2]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    rename_column_concurrently :design_management_versions, :user_id, :author_id
+  end
+
+  def down
+    undo_rename_column_concurrently :design_management_versions, :user_id, :author_id
+  end
+end

db/migrate/20191014030730_add_author_index_to_design_management_versions.rb

+# frozen_string_literal: true
+
+class AddAuthorIndexToDesignManagementVersions < ActiveRecord::Migration[5.2]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_index :design_management_versions, :author_id, where: 'author_id IS NOT NULL'
+  end
+
+  def down
+    remove_concurrent_index :design_management_versions, :author_id
+  end
+end

db/post_migrate/20191014030134_cleanup_design_management_version_user_to_author_rename.rb

+# frozen_string_literal: true
+
+class CleanupDesignManagementVersionUserToAuthorRename < ActiveRecord::Migration[5.2]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    cleanup_concurrent_column_rename :design_management_versions, :user_id, :author_id
+  end
+
+  def down
+    undo_cleanup_concurrent_column_rename :design_management_versions, :user_id, :author_id
+  end
+end

db/schema.rb

@@ -1287,11 +1287,11 @@ ActiveRecord::Schema.define(version: 2019_10_16_220135) do
   create_table "design_management_versions", force: :cascade do |t|
     t.binary "sha", null: false
     t.bigint "issue_id"
-    t.integer "user_id"
     t.datetime_with_timezone "created_at"
+    t.integer "author_id"
+    t.index ["author_id"], name: "index_design_management_versions_on_author_id", where: "(author_id IS NOT NULL)"
     t.index ["issue_id"], name: "index_design_management_versions_on_issue_id"
     t.index ["sha", "issue_id"], name: "index_design_management_versions_on_sha_and_issue_id", unique: true
-    t.index ["user_id"], name: "index_design_management_versions_on_user_id", where: "(user_id IS NOT NULL)"
   end
 
   create_table "draft_notes", force: :cascade do |t|
@@ -4094,7 +4094,7 @@ ActiveRecord::Schema.define(version: 2019_10_16_220135) do
   add_foreign_key "design_management_designs_versions", "design_management_designs", column: "design_id", name: "fk_03c671965c", on_delete: :cascade
   add_foreign_key "design_management_designs_versions", "design_management_versions", column: "version_id", name: "fk_f4d25ba00c", on_delete: :cascade
   add_foreign_key "design_management_versions", "issues", on_delete: :cascade
-  add_foreign_key "design_management_versions", "users", name: "fk_ee16b939e5", on_delete: :nullify
+  add_foreign_key "design_management_versions", "users", column: "author_id", name: "fk_c1440b4896", on_delete: :nullify
   add_foreign_key "draft_notes", "merge_requests", on_delete: :cascade
   add_foreign_key "draft_notes", "users", column: "author_id", on_delete: :cascade
   add_foreign_key "elasticsearch_indexed_namespaces", "namespaces", on_delete: :cascade

ee/changelogs/unreleased/13426-rename-design-management-version-user_id-to-author_id.yml

+---
+title: Rename user_id to author_id in design_management_versions table
+merge_request: 18506
+author:
+type: other

spec/lib/gitlab/import_export/safe_model_attributes.yml

@@ -752,4 +752,4 @@ DesignManagement::Version:
 - created_at
 - sha
 - issue_id
-- user_id
+- author_id