Add Group migration imports to usage data

We want to be able to report on how many unique users are using the
BulkImport feature, so that we can determine the adoption rate of this
feature.

Add this data to the usage data model that is reported in the usage
ping.

Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/249169
MR: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/45536

changelogs/unreleased/jh-migration_mvc_gmau.yml

+---
+title: Add usage ping for unique users importing groups and projects via the group
+  migration tool
+merge_request: 45536
+author:
+type: changed

lib/gitlab/usage_data.rb

@@ -564,6 +564,9 @@ module Gitlab
           users_created: count(::User.where(time_period), start: user_minimum_id, finish: user_maximum_id),
           omniauth_providers: filtered_omniauth_provider_names.reject { |name| name == 'group_saml' },
           user_auth_by_provider: distinct_count_user_auth_by_provider(time_period),
+          bulk_imports: {
+            gitlab: distinct_count(::BulkImport.where(time_period, source_type: :gitlab), :user_id)
+          },
           projects_imported: {
             gitlab_project: projects_imported_count('gitlab_project', time_period),
             gitlab: projects_imported_count('gitlab', time_period),

spec/lib/gitlab/usage_data_spec.rb

@@ -201,6 +201,8 @@ RSpec.describe Gitlab::UsageData, :aggregate_failures do
       for_defined_days_back do
         user = create(:user)
 
+        create(:bulk_import, user: user)
+
         %w(gitlab_project gitlab github bitbucket bitbucket_server gitea git manifest fogbugz phabricator).each do |type|
           create(:project, import_type: type, creator_id: user.id)
         end
@@ -211,6 +213,9 @@ RSpec.describe Gitlab::UsageData, :aggregate_failures do
 
       expect(described_class.usage_activity_by_stage_manage({})).to include(
         {
+          bulk_imports: {
+            gitlab: 2
+          },
           projects_imported: {
             gitlab_project: 2,
             gitlab: 2,
@@ -230,6 +235,9 @@ RSpec.describe Gitlab::UsageData, :aggregate_failures do
       )
       expect(described_class.usage_activity_by_stage_manage(described_class.last_28_days_time_period)).to include(
         {
+          bulk_imports: {
+            gitlab: 1
+          },
           projects_imported: {
             gitlab_project: 1,
             gitlab: 1,