Convert datetime field to datetime_local (#8572)

* Convert datetime field to datetime_local

* Fix tests

* Add value formatting view datetime component

* Add helper datetime component value

spec/components/editable_champ/datetime_component/datetime_component_spec.rb

@@ -0,0 +1,27 @@
+describe EditableChamp::DatetimeComponent, type: :component do
+  let(:component) {
+    described_class.new(form: instance_double(ActionView::Helpers::FormBuilder, object_name: "dossier[champs_public_attributes]"), champ:)
+  }
+
+  describe '#formatted_value_for_datetime_locale' do
+    subject { component.formatted_value_for_datetime_locale }
+
+    context 'when the value is nil' do
+      let(:champ) { create(:champ_datetime, dossier: create(:dossier), value: nil) }
+
+      it { is_expected.to be_nil }
+    end
+
+    context 'when the value is not a valid datetime' do
+      let(:champ) { create(:champ_datetime, dossier: create(:dossier), value: 'invalid') }
+
+      it { is_expected.to be_nil }
+    end
+
+    context 'when the value is a valid datetime' do
+      let(:champ) { create(:champ_datetime, dossier: create(:dossier), value: '2020-01-01T00:00:00+01:00') }
+
+      it { is_expected.to eq('2020-01-01T00:00') }
+    end
+  end
+end