asp: truncate the persphysique names attributes

Piggyback the `limit` option for ActiveModel's attribute method (which
might be a thing one day[1]) to chop the value of the string directly
on the XML-generating class.

This keeps the mapping classes in charge of translating our data into
the ASP stuff, semantically, but keeps the actual XML-maker in control
of the formatted length, which makes more sense to me: all the XML
tags have an associated length in the ASP documentation, so keeping it
as close as possible to the XML generation code is nicer.

Closes #678.

[1]: rails/rails#51494

config/initializers/types.rb

@@ -8,4 +8,18 @@ def cast(value)
   end
 end
 
+module ActiveModel
+  module Type
+    class String
+      def cast(value)
+        if @limit
+          super(value.to_s.first(@limit))
+        else
+          super
+        end
+      end
+    end
+  end
+end
+
 ActiveModel::Type.register :asp_date, AspDateType

lib/asp/entities/pers_physique.rb

@@ -3,11 +3,14 @@
 module ASP
   module Entities
     class PersPhysique < Entity
+      FIRST_NAME_MAX_LENGTH = 20
+      LAST_NAME_MAX_LENGTH  = 50
+
       attribute :titre, :string
-      attribute :nomusage, :string
-      attribute :nomnaissance, :string
-      attribute :prenom, :string
-      attribute :datenaissance, :date
+      attribute :nomusage, :string, limit: LAST_NAME_MAX_LENGTH
+      attribute :nomnaissance, :string, limit: LAST_NAME_MAX_LENGTH
+      attribute :prenom, :string, limit: FIRST_NAME_MAX_LENGTH
+      attribute :datenaissance
       attribute :codeinseepaysnai, :string
       attribute :codeinseecommune, :string
 

spec/lib/asp/entities/pers_physique_spec.rb

@@ -15,6 +15,10 @@
   describe "validation" do
     subject(:model) { described_class.from_payment_request(payment_request) }
 
+    it_behaves_like "a limited string attribute", attribute: :prenom, length: 20
+    it_behaves_like "a limited string attribute", attribute: :nomnaissance, length: 50
+    it_behaves_like "a limited string attribute", attribute: :nomusage, length: 50
+
     context "when the student is born in France" do
       let(:student) { create(:student, :with_extra_info, :born_in_france) }
 

spec/support/shared/attribute_limiter.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+require "rails_helper"
+
+RSpec.shared_examples "a limited string attribute" do |attribute:, length:|
+  it "chops the '#{attribute}' attribute to #{length} characters" do
+    model.send "#{attribute}=", Faker::Alphanumeric.alpha(number: length + 1)
+
+    expect(model.send(attribute).to_s).to have(length).characters
+  end
+end