Improve contact phone number validation

#569

spec/lib/e164_phone_number.rb

@@ -0,0 +1,29 @@
+# https://en.wikipedia.org/wiki/E.164
+
+RSpec.shared_examples 'e164 phone number' do
+  describe 'validation' do
+    it 'rejects invalid format' do
+      model.send("#{attribute}=", '+.1')
+      model.validate
+      expect(model.errors).to be_added(attribute, :invalid)
+    end
+
+    it 'rejects longer than max length' do
+      model.send("#{attribute}=", '1' * 18)
+      model.validate
+      expect(model.errors).to be_added(attribute, :too_long, count: 17)
+    end
+
+    it 'accepts valid format' do
+      model.send("#{attribute}=", '+123.4')
+      model.validate
+      expect(model.errors).to_not be_added(attribute, :invalid)
+    end
+
+    it 'accepts max length' do
+      model.send("#{attribute}=", '1' * 17)
+      model.validate
+      expect(model.errors).to_not be_added(attribute, :too_long, count: 17)
+    end
+  end
+end