Fix missing attributes for import_export

Squashed commits:
 - Fix rubocop offences
 - Parametrized rspec testing all relation paths
 - Use AttributeCleaner instead duplicating code
 - Add changelog for strong validation
 - Add frozen string literal for references
 - Add excluded attributes to configuration

changelogs/unreleased/strong-validate-import-export-references.yml

+---
+title: Strong validate import export references
+merge_request: 19682
+author:
+type: added

lib/gitlab/import_export/import_export.yml

@@ -185,6 +185,7 @@ excluded_attributes:
     - :moved_to_id
     - :state_id
     - :duplicated_to_id
+    - :promoted_to_epic_id
   merge_request:
     - :milestone_id
     - :ref_fetched
@@ -222,6 +223,8 @@ excluded_attributes:
     - :upstream_pipeline_id
     - :resource_group_id
     - :waiting_for_resource_at
+  sentry_issue:
+    - :issue_id
   push_event_payload:
     - :event_id
   project_badges:
@@ -262,6 +265,8 @@ excluded_attributes:
     - :issue_id
   zoom_meetings:
     - :issue_id
+  design:
+    - :issue_id
   designs:
     - :issue_id
   design_versions:
@@ -287,7 +292,20 @@ excluded_attributes:
     - :pipeline_id
   merge_access_levels:
     - :protected_branch_id
-
+  push_access_levels:
+    - :protected_branch_id
+  unprotect_access_levels:
+    - :protected_branch_id
+  create_access_levels:
+    - :protected_tag_id
+  deploy_access_levels:
+    - :protected_environment_id
+  boards:
+    - :milestone_id
+  lists:
+    - :board_id
+    - :label_id
+    - :milestone_id
 methods:
   notes:
     - :type

spec/lib/gitlab/import_export/attribute_configuration_spec.rb

@@ -16,7 +16,7 @@ describe 'Import/Export attribute configuration' do
   let(:safe_model_attributes) { YAML.load_file(safe_attributes_file) }
 
   it 'has no new columns' do
-    relation_names.each do |relation_name|
+    project_relation_names.each do |relation_name|
       relation_class = relation_class_for_name(relation_name)
       relation_attributes = relation_class.new.attributes.keys - relation_class.encrypted_attributes.keys.map(&:to_s)
 

spec/lib/gitlab/import_export/model_configuration_spec.rb

@@ -11,7 +11,7 @@ describe 'Import/Export model configuration' do
   let(:all_models_yml) { 'spec/lib/gitlab/import_export/all_models.yml' }
   let(:all_models_hash) { YAML.load_file(all_models_yml) }
   let(:current_models) { setup_models }
-  let(:model_names) { relation_names }
+  let(:model_names) { project_relation_names }
 
   it 'has no new models' do
     model_names.each do |model_name|

spec/lib/gitlab/import_export/references_configuration_spec.rb

+# frozen_string_literal: true
+
 require 'spec_helper'
 
 # Part of the test security suite for the Import/Export feature
@@ -7,22 +9,28 @@ require 'spec_helper'
 # or to be blacklisted by using the import_export.yml configuration file.
 # Likewise, new models added to import_export.yml, will need to be added with their correspondent relations
 # to this spec.
-describe 'Import/Export references configuration' do
+describe 'Import/Export Project configuration' do
   include ConfigurationHelper
 
-  it 'has no prohibited keys' do
-    relation_names.each do |relation_name|
+  where(:relation_path, :relation_name) do
+    project_relation_paths.map {|a| [a.join("."), a.last]}
+  end
+
+  with_them do
+    next if params[:relation_name] == "author"
+
+    context "where relation #{params[:relation_path]}" do
+      it 'does not have prohibited keys' do
         relation_class = relation_class_for_name(relation_name)
         relation_attributes = relation_class.new.attributes.keys - relation_class.encrypted_attributes.keys.map(&:to_s)
         current_attributes = parsed_attributes(relation_name, relation_attributes)
-
         prohibited_keys = current_attributes.select do |attribute|
           prohibited_key?(attribute) || !relation_class.attribute_method?(attribute)
         end
-
         expect(prohibited_keys).to be_empty, failure_message(relation_class.to_s, prohibited_keys)
       end
     end
+  end
 
   def failure_message(relation_class, prohibited_keys)
     <<-MSG

spec/support/import_export/configuration_helper.rb

 # frozen_string_literal: true
 
 module ConfigurationHelper
-  ALLOWED_REFERENCES = Gitlab::ImportExport::RelationFactory::PROJECT_REFERENCES + Gitlab::ImportExport::RelationFactory::USER_REFERENCES + %w[group_id commit_id]
-  PROHIBITED_REFERENCES = Regexp.union(/\Acached_markdown_version\Z/, /_id\Z/, /_html\Z/).freeze
-
   # Returns a list of models from hashes/arrays contained in +project_tree+
   def names_from_tree(project_tree)
     project_tree.map do |branch_or_model|
@@ -13,17 +10,34 @@ module ConfigurationHelper
     end
   end
 
+  # - flattens hash to list all relation paths
+  def flat_hash(hash, path = [])
+    new_hash = {}
+    hash.each_pair do |key, val|
+      new_hash[path + [key]] = val
+      if val.is_a?(Hash) && val.present?
+        new_hash.merge!(flat_hash(val, path + [key]))
+      end
+    end
+    new_hash
+  end
+
   def config_hash
     Gitlab::ImportExport::Config.new.to_h.deep_stringify_keys
   end
 
-  def relation_names
+  def project_relation_paths
+    # - project is not part of the tree, so it has to be added manually.
+    flat_hash({ "project" => config_hash.dig('tree', 'project') }).keys
+  end
+
+  def project_relation_names
     names = names_from_tree(config_hash.dig('tree', 'project'))
     # Remove duplicated or add missing models
     # - project is not part of the tree, so it has to be added manually.
     # - milestone, labels, merge_request have both singular and plural versions in the tree, so remove the duplicates.
     # - User, Author... Models we do not care about for checking models
-    names.flatten.uniq - %w(milestones labels user author merge_request) + ['project']
+    names.flatten.uniq - %w(milestones labels user author merge_request design) + ['project']
   end
 
   def relation_class_for_name(relation_name)
@@ -40,11 +54,11 @@ module ConfigurationHelper
   end
 
   def prohibited_key?(key)
-    key =~ PROHIBITED_REFERENCES && !permitted_key?(key)
+    key =~ Gitlab::ImportExport::AttributeCleaner::PROHIBITED_REFERENCES && !permitted_key?(key)
   end
 
   def permitted_key?(key)
-    ALLOWED_REFERENCES.include?(key)
+    Gitlab::ImportExport::AttributeCleaner::ALLOWED_REFERENCES.include?(key)
   end
 
   def associations_for(safe_model)