Add license encryption key for testing purposes

There's only one encryption key for licenses at the moment. In order to
encrypt licenses that were created for testing purposes, a new
encryption key is introduced.

.test_license_encryption_key.pub

+-----BEGIN PUBLIC KEY-----
+MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAtgemxR8RUJXi3p7G/dkh
+Yuln1L4lA6GtQsT83X0yTVDbLVsI2C6bepsRjGiLV0R/9JGvTojORx+9F/ZQAiEC
+g6QXWasAOSmrzr4EjADG6cWcCnOju8hX9yib1HUIBxl+jHkmXP3NPuwyb8p2G149
+EG1o4apEqE5RtqV/Xyx/u57xTYYZShJ/c7o4iA8xvt6IAKFPFKpQwb5hv4KvUZBP
+h0xG2qvOjDu430fK8JclPlXHqPjXDkXOZyLd4FvRStdEQU3RVXvUQfuGt/tOMS7J
+nPQ94fr/xdaEbcEtIlr32+tcgsMWyhqtDCPUWJT1aRPviUgaJKLoVs8tRKwYMV9+
+1wIDAQAB
+-----END PUBLIC KEY-----

config/initializers/0_license.rb

 # frozen_string_literal: true
 
 Gitlab.ee do
-  public_key_file = File.read(Rails.root.join(".license_encryption_key.pub"))
+  prefix = ENV['GITLAB_LICENSE_MODE'] == 'test' ? 'test_' : ''
+  public_key_file = File.read(Rails.root.join(".#{prefix}license_encryption_key.pub"))
   public_key = OpenSSL::PKey::RSA.new(public_key_file)
   Gitlab::License.encryption_key = public_key
 rescue

ee/app/models/license.rb

@@ -286,7 +286,8 @@ class License < ApplicationRecord
     end
 
     def history
-      all.sort_by { |license| [license.starts_at, license.created_at, license.expires_at] }.reverse
+      decryptable_licenses = all.select { |license| license.license.present? }
+      decryptable_licenses.sort_by { |license| [license.starts_at, license.created_at, license.expires_at] }.reverse
     end
 
     private

ee/changelogs/unreleased/use_testing_license_key.yml

+---
+title: Add license encryption key for testing purposes
+merge_request: 42475
+author:
+type: added

ee/spec/models/license_spec.rb

@@ -849,8 +849,18 @@ RSpec.describe License do
       described_class.delete_all
     end
 
+    let_it_be(:today) { Date.current }
+
+    it 'does not include the undecryptable license' do
+      undecryptable_license = create(:license, created_at: today)
+      allow(undecryptable_license).to receive(:license).and_return(nil)
+
+      allow(License).to receive(:all).and_return([undecryptable_license])
+
+      expect(described_class.history.map(&:id)).to be_empty
+    end
+
     it 'returns the licenses sorted by created_at, starts_at and expires_at descending' do
-      today = Date.current
       now = Time.current
 
       past_license = create(:license, created_at: now - 1.month, data: build(:gitlab_license, starts_at: today - 1.month, expires_at: today + 11.months).export)