Load spec helpers before Rails is loaded

Using Spring was hiding an loading error. When you start Rspec, Rails
and its engines are not loaded yet. So our way to load the spec helper
via `Rails.root` did not work when you ran specs on their own without
loading Rails with Spring first.

engines/dfc_provider/spec/requests/catalog_items_spec.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require DfcProvider::Engine.root.join("spec/swagger_helper")
+require_relative "../swagger_helper"
 
 describe "CatalogItems", type: :request, swagger_doc: "dfc-v1.7/swagger.yaml",
                          rswag_autodoc: true do

engines/dfc_provider/spec/requests/enterprises_spec.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require DfcProvider::Engine.root.join("spec/swagger_helper")
+require_relative "../swagger_helper"
 
 describe "Enterprises", type: :request, swagger_doc: "dfc-v1.7/swagger.yaml", rswag_autodoc: true do
   let!(:user) { create(:oidc_user) }

engines/dfc_provider/spec/requests/persons_spec.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require DfcProvider::Engine.root.join("spec/swagger_helper")
+require_relative "../swagger_helper"
 
 describe "Persons", type: :request, swagger_doc: "dfc-v1.7/swagger.yaml", rswag_autodoc: true do
   let(:user) { create(:oidc_user, id: 10_000) }

engines/dfc_provider/spec/requests/supplied_products_spec.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require DfcProvider::Engine.root.join("spec/swagger_helper")
+require_relative "../swagger_helper"
 
 describe "SuppliedProducts", type: :request, swagger_doc: "dfc-v1.7/swagger.yaml",
                              rswag_autodoc: true do

engines/dfc_provider/spec/services/authorization_control_spec.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require DfcProvider::Engine.root.join("spec/spec_helper")
+require_relative "../spec_helper"
 
 describe AuthorizationControl do
   include AuthorizationHelper

engines/dfc_provider/spec/services/catalog_item_builder_spec.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require DfcProvider::Engine.root.join("spec/spec_helper")
+require_relative "../spec_helper"
 
 describe DfcBuilder do
   let(:variant) { build(:variant) }

engines/dfc_provider/spec/services/dfc_io_spec.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require DfcProvider::Engine.root.join("spec/spec_helper")
+require_relative "../spec_helper"
 
 describe DfcIo do
   let(:person) do

engines/dfc_provider/spec/services/dfc_loader_spec.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require DfcProvider::Engine.root.join("spec/spec_helper")
+require_relative "../spec_helper"
 
 describe DfcLoader do
   it "prepares the DFC Connector to provide DFC object classes for export" do

engines/dfc_provider/spec/services/enterprise_builder_spec.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require DfcProvider::Engine.root.join("spec/spec_helper")
+require_relative "../spec_helper"
 
 describe EnterpriseBuilder do
   subject(:builder) { described_class }

engines/dfc_provider/spec/services/offer_builder_spec.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require DfcProvider::Engine.root.join("spec/spec_helper")
+require_relative "../spec_helper"
 
 describe DfcBuilder do
   let(:variant) { build(:variant) }

engines/dfc_provider/spec/services/quantitative_value_builder_spec.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require DfcProvider::Engine.root.join("spec/spec_helper")
+require_relative "../spec_helper"
 
 describe QuantitativeValueBuilder do
   subject(:builder) { described_class }

engines/dfc_provider/spec/services/supplied_product_builder_spec.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require DfcProvider::Engine.root.join("spec/spec_helper")
+require_relative "../spec_helper"
 
 describe SuppliedProductBuilder do
   subject(:builder) { described_class }

engines/dfc_provider/spec/swagger_helper.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require Rails.root.join("spec/swagger_helper")
+require_relative "../../../spec/swagger_helper"
 require_relative "spec_helper"
 
 RSpec.configure do |config|