Add additional instructions for personal billing page

- Add context to assist users in creating and/or moving a project
  to a group.

- refs: https://gitlab.com/gitlab-org/gitlab/-/issues/352629
        https://gitlab.com/gitlab-org/gitlab/-/merge_requests/82738#note_894049190

ee/app/helpers/billing_plans_helper.rb

@@ -168,6 +168,36 @@ module BillingPlansHelper
     }
   end
 
+  def add_namespace_plan_to_group_instructions
+    link_end = '</a>'.html_safe
+
+    move_link_url = help_page_path 'user/project/settings/index',
+                                   anchor: "transferring-an-existing-project-into-another-namespace"
+
+    move_link_start = '<a href="%{url}" target="_blank" rel="noopener noreferrer">'.html_safe % { url: move_link_url }
+
+    if current_user.owned_or_maintainers_groups.any?
+      html_escape_once(
+        s_("BillingPlans|You'll have to %{move_link_start}move this project%{move_link_end} to one of your groups.")
+      ).html_safe % {
+        move_link_start: move_link_start,
+        move_link_end: link_end
+      }
+    else
+      create_group_link_url = new_group_path anchor: "create-group-pane"
+      create_group_link_start = '<a href="%{url}">'.html_safe % { url: create_group_link_url }
+
+      html_escape_once(
+        s_("BillingPlans|You don't have any groups. You'll need to %{create_group_link_start}create one%{create_group_link_end} and %{move_link_start}move this project to it%{move_link_end}.")
+      ).html_safe % {
+        create_group_link_start: create_group_link_start,
+        create_group_link_end: link_end,
+        move_link_start: move_link_start,
+        move_link_end: link_end
+      }
+    end
+  end
+
   private
 
   def add_seats_url(group)

ee/app/views/shared/billings/_billing_plan_header.html.haml

@@ -23,6 +23,8 @@
   - if namespace.free_personal?
     - groups_link = link_to s_("BillingPlans|group"), dashboard_groups_path
     %p= html_escape_once(s_("BillingPlans|Looking to purchase or manage a subscription for your group? Navigate to your %{groups_link} and go to %{strong_open}Settings &gt; Billing.%{strong_close}")).html_safe % { groups_link: groups_link.html_safe, strong_open: '<strong>'.html_safe, strong_close: '</strong>'.html_safe }
+    %p.gl-mt-1
+      = add_namespace_plan_to_group_instructions
   - elsif parent_group
     %p= s_("BillingPlans|This group uses the plan associated with its parent group.")
     - parent_billing_page_link = link_to parent_group.full_name, group_billings_path(parent_group)

ee/spec/features/profiles/billing_spec.rb

@@ -42,6 +42,24 @@ RSpec.describe 'Profiles > Billing', :js do
 
         expect(page).not_to have_field(placeholder: SearchHelpers::INPUT_PLACEHOLDER)
       end
+
+      context "wtihout a group" do
+        it 'displays help for moving groups' do
+          visit profile_billings_path
+
+          expect(page).to have_content "You don't have any groups."
+        end
+      end
+
+      context "with a maintained or owned group" do
+        it 'displays help for moving groups' do
+          create(:group).add_owner user
+          visit profile_billings_path
+
+          expect(page).not_to have_content "You don't have any groups"
+          expect(page).to have_content "You'll have to move this project"
+        end
+      end
     end
   end
 end

ee/spec/helpers/billing_plans_helper_spec.rb

@@ -590,4 +590,26 @@ RSpec.describe BillingPlansHelper, :saas do
       expect(helper.start_free_trial_data).to eq data
     end
   end
+
+  describe '#add_namespace_plan_to_group_instructions' do
+    let_it_be(:current_user) { create :user }
+
+    before do
+      allow(helper).to receive(:current_user).and_return(current_user)
+    end
+
+    context 'with maintained or owned group' do
+      it 'instructs to move the project to a group' do
+        create(:group).add_owner current_user
+
+        expect(helper.add_namespace_plan_to_group_instructions).to eq 'You&#39;ll have to <a href="/help/user/project/settings/index#transferring-an-existing-project-into-another-namespace" target="_blank" rel="noopener noreferrer">move this project</a> to one of your groups.'
+      end
+    end
+
+    context 'without a group' do
+      it 'instructs to create a group then move the project to a group' do
+        expect(helper.add_namespace_plan_to_group_instructions).to eq 'You don&#39;t have any groups. You&#39;ll need to <a href="/groups/new#create-group-pane">create one</a> and <a href="/help/user/project/settings/index#transferring-an-existing-project-into-another-namespace" target="_blank" rel="noopener noreferrer">move this project to it</a>.'
+      end
+    end
+  end
 end

locale/gitlab.pot

@@ -5686,6 +5686,12 @@ msgstr ""
 msgid "BillingPlans|While GitLab is ending availability of the Bronze plan, you can still renew your Bronze subscription one additional time before %{eoa_bronze_plan_end_date}. We are also offering a limited time free upgrade to our Premium Plan (up to 25 users)! Learn more about the changes and offers in our %{announcement_link}."
 msgstr ""
 
+msgid "BillingPlans|You don't have any groups. You'll need to %{create_group_link_start}create one%{create_group_link_end} and %{move_link_start}move this project to it%{move_link_end}."
+msgstr ""
+
+msgid "BillingPlans|You'll have to %{move_link_start}move this project%{move_link_end} to one of your groups."
+msgstr ""
+
 msgid "BillingPlans|Your GitLab.com %{plan} trial will %{strong_open}expire after %{expiration_date}%{strong_close}. You can retain access to the %{plan} features by upgrading below."
 msgstr ""