feat: add email validation

app/services/customers/create_service.rb

@@ -9,6 +9,13 @@ def create_from_api(organization:, params:)
       new_customer = customer.new_record?
       shipping_address = params[:shipping_address] ||= {}
 
+      unless valid_email?(params[:email])
+        return result.single_validation_failure!(
+          field: :email,
+          error_code: 'invalid_format'
+        )
+      end
+
       unless valid_metadata_count?(metadata: params[:metadata])
         return result.single_validation_failure!(
           field: :metadata,
@@ -187,6 +194,13 @@ def create(**args)
 
     private
 
+    def valid_email?(email)
+      return true if email.nil?
+
+      email_regexp = /\A[^@\s]+@[^@\s]+\z/
+      email_regexp.match?(email).present?
+    end
+
     def valid_metadata_count?(metadata:)
       return true if metadata.blank?
       return true if metadata.count <= ::Metadata::CustomerMetadata::COUNT_PER_CUSTOMER

spec/services/customers/create_service_spec.rb

@@ -104,6 +104,43 @@
       )
     end
 
+    context 'with invalid email' do
+      let(:create_args) do
+        {
+          external_id:,
+          name: 'Foo Bar',
+          currency: 'EUR',
+          email: '@missingusername.com',
+          tax_identification_number: '123456789',
+          billing_configuration: {
+            document_locale: 'fr'
+          },
+          shipping_address: {
+            address_line1: 'line1',
+            address_line2: 'line2',
+            city: 'Paris',
+            zipcode: '123456',
+            state: 'foobar',
+            country: 'FR'
+          }
+        }
+      end
+
+      it 'fails to create customer with wrong email' do
+        result = customers_service.create_from_api(
+          organization:,
+          params: create_args
+        )
+
+        aggregate_failures do
+          expect(result).not_to be_success
+          expect(result.error).to be_a(BaseService::ValidationFailure)
+          expect(result.error.messages.keys).to include(:email)
+          expect(result.error.messages[:email]).to include('invalid_format')
+        end
+      end
+    end
+
     context 'with external_id already used by a deleted customer' do
       it 'creates a customer with the same external_id' do
         create(:customer, :deleted, organization:, external_id:)