Create BulkImport model to group import models

We want to start importing Group and Project data directly from
another GitLab instance, via the API. To do this, we need somewhere
to store authentication data, entity mapping data and other metadata
so that we can perform the import in background jobs.

Create the BulkImport model which is associated with a user, and used to
group together all the data relating to the one bulk import request from
the user. This will be followed up by the introduction of the other
models the store the import data.

This model introduces:

1. `source_type` -> where the data for this import is being sourced
   from. For now this will just be GitLab imports, but in the future we
   could expand this structure to other services like GitHub and
   Bitbucket.
2. `user_id` -> the user that initiated the import.
3. `status` -> to be used by the state machine for recording the status
   of the overall import.

This is a component of the Group Migration MVC epic:
https://gitlab.com/groups/gitlab-org/-/epics/4374

MR: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/42978
Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/250280

app/models/bulk_import.rb

+# frozen_string_literal: true
+
+class BulkImport < ApplicationRecord
+  belongs_to :user, optional: false
+
+  validates :source_type, :status, presence: true
+
+  enum source_type: { gitlab: 0 }
+
+  state_machine :status, initial: :created do
+    state :created, value: 0
+  end
+end

app/models/user.rb

@@ -167,6 +167,8 @@ class User < ApplicationRecord
   has_many :assigned_issues, class_name: "Issue", through: :issue_assignees, source: :issue
   has_many :assigned_merge_requests, class_name: "MergeRequest", through: :merge_request_assignees, source: :merge_request
 
+  has_many :bulk_imports
+
   has_many :custom_attributes, class_name: 'UserCustomAttribute'
   has_many :callouts, class_name: 'UserCallout'
   has_many :term_agreements

changelogs/unreleased/jh-store_temp_import_data.yml

+---
+title: Create a set of models to store the temporary data needed for a bulk import
+merge_request: 42978
+author:
+type: changed

db/migrate/20200922133949_create_bulk_import.rb

+# frozen_string_literal: true
+
+class CreateBulkImport < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  def up
+    with_lock_retries do
+      create_table :bulk_imports do |t|
+        t.references :user, type: :integer, index: true, null: false, foreign_key: { on_delete: :cascade }
+
+        t.integer :source_type, null: false, limit: 2
+        t.integer :status, null: false, limit: 2
+
+        t.timestamps_with_timezone
+      end
+    end
+  end
+
+  def down
+    with_lock_retries do
+      drop_table :bulk_imports
+    end
+  end
+end

db/schema_migrations/20200922133949

+8196e28f6fe8cdb4cf710922b5cd218030ba587c629de7ee75dc061d05c7e1a9
\ No newline at end of file

db/structure.sql

@@ -9816,6 +9816,24 @@ CREATE SEQUENCE broadcast_messages_id_seq
 
 ALTER SEQUENCE broadcast_messages_id_seq OWNED BY broadcast_messages.id;
 
+CREATE TABLE bulk_imports (
+    id bigint NOT NULL,
+    user_id integer NOT NULL,
+    source_type smallint NOT NULL,
+    status smallint NOT NULL,
+    created_at timestamp with time zone NOT NULL,
+    updated_at timestamp with time zone NOT NULL
+);
+
+CREATE SEQUENCE bulk_imports_id_seq
+    START WITH 1
+    INCREMENT BY 1
+    NO MINVALUE
+    NO MAXVALUE
+    CACHE 1;
+
+ALTER SEQUENCE bulk_imports_id_seq OWNED BY bulk_imports.id;
+
 CREATE TABLE chat_names (
     id integer NOT NULL,
     user_id integer NOT NULL,
@@ -17304,6 +17322,8 @@ ALTER TABLE ONLY boards_epic_user_preferences ALTER COLUMN id SET DEFAULT nextva
 
 ALTER TABLE ONLY broadcast_messages ALTER COLUMN id SET DEFAULT nextval('broadcast_messages_id_seq'::regclass);
 
+ALTER TABLE ONLY bulk_imports ALTER COLUMN id SET DEFAULT nextval('bulk_imports_id_seq'::regclass);
+
 ALTER TABLE ONLY chat_names ALTER COLUMN id SET DEFAULT nextval('chat_names_id_seq'::regclass);
 
 ALTER TABLE ONLY chat_teams ALTER COLUMN id SET DEFAULT nextval('chat_teams_id_seq'::regclass);
@@ -18280,6 +18300,9 @@ ALTER TABLE ONLY boards
 ALTER TABLE ONLY broadcast_messages
     ADD CONSTRAINT broadcast_messages_pkey PRIMARY KEY (id);
 
+ALTER TABLE ONLY bulk_imports
+    ADD CONSTRAINT bulk_imports_pkey PRIMARY KEY (id);
+
 ALTER TABLE ONLY chat_names
     ADD CONSTRAINT chat_names_pkey PRIMARY KEY (id);
 
@@ -19785,6 +19808,8 @@ CREATE INDEX index_boards_on_project_id ON boards USING btree (project_id);
 
 CREATE INDEX index_broadcast_message_on_ends_at_and_broadcast_type_and_id ON broadcast_messages USING btree (ends_at, broadcast_type, id);
 
+CREATE INDEX index_bulk_imports_on_user_id ON bulk_imports USING btree (user_id);
+
 CREATE UNIQUE INDEX index_chat_names_on_service_id_and_team_id_and_chat_id ON chat_names USING btree (service_id, team_id, chat_id);
 
 CREATE UNIQUE INDEX index_chat_names_on_user_id_and_service_id ON chat_names USING btree (user_id, service_id);
@@ -22835,6 +22860,9 @@ ALTER TABLE ONLY project_statistics
 ALTER TABLE ONLY user_details
     ADD CONSTRAINT fk_rails_12e0b3043d FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE;
 
+ALTER TABLE ONLY bulk_imports
+    ADD CONSTRAINT fk_rails_130a09357d FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE;
+
 ALTER TABLE ONLY diff_note_positions
     ADD CONSTRAINT fk_rails_13c7212859 FOREIGN KEY (note_id) REFERENCES notes(id) ON DELETE CASCADE;
 

spec/factories/bulk_import.rb

+# frozen_string_literal: true
+
+FactoryBot.define do
+  factory :bulk_import, class: 'BulkImport' do
+    user
+    source_type { :gitlab }
+  end
+end

spec/models/bulk_import_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe BulkImport, type: :model do
+  describe 'associations' do
+    it { is_expected.to belong_to(:user).required }
+  end
+
+  describe 'validations' do
+    it { is_expected.to validate_presence_of(:source_type) }
+    it { is_expected.to validate_presence_of(:status) }
+
+    it { is_expected.to define_enum_for(:source_type).with_values(%i[gitlab]) }
+  end
+end