Replace api controller test helpers with easier existing alternatives

spec/controllers/api/product_images_controller_spec.rb

@@ -14,8 +14,7 @@ module Api
       let(:image) { Rack::Test::UploadedFile.new(image_path, 'image/png') }
       let!(:product_without_image) { create(:product) }
       let!(:product_with_image) { create(:product_with_image) }
-
-      sign_in_as_admin!
+      let(:current_api_user) { create(:admin_user) }
 
       it "saves a new image when none is present" do
         xhr :post, :update_product_image, product_id: product_without_image.id, file: image, use_route: :product_images

spec/controllers/api/variants_controller_spec.rb

@@ -84,7 +84,7 @@ describe Api::VariantsController, type: :controller do
   end
 
   context "as an enterprise user" do
-    sign_in_as_enterprise_user! [:supplier]
+    let(:current_api_user) { create(:user, enterprises: [supplier]) }
     let(:supplier_other) { create(:supplier_enterprise) }
     let(:product) { create(:product, supplier: supplier) }
     let(:variant) { product.master }
@@ -109,7 +109,7 @@ describe Api::VariantsController, type: :controller do
   end
 
   context "as an administrator" do
-    sign_in_as_admin!
+    let(:current_api_user) { create(:admin_user) }
 
     let(:product) { create(:product) }
     let(:variant) { product.master }