tasks: add progress report to the pjs migration task

Progress is indicated per migrated champ.

spec/services/piece_justificative_to_champ_piece_jointe_migration_service_spec.rb

@@ -9,16 +9,17 @@ describe PieceJustificativeToChampPieceJointeMigrationService do
   let(:procedure) { create(:procedure, types_de_piece_justificative: types_pj) }
   let(:types_pj) { [create(:type_de_piece_justificative)] }
 
-  let!(:dossier) do
-    create(
-      :dossier,
-      procedure: procedure,
-      pieces_justificatives: pjs
-    )
-  end
+  let!(:dossier) { make_dossier }
 
   let(:pjs) { [] }
 
+  def make_dossier(hidden: false)
+    create(:dossier,
+      procedure: procedure,
+      pieces_justificatives: pjs,
+      hidden_at: hidden ? Time.zone.now : nil)
+  end
+
   def make_pjs
     types_pj.map do |tpj|
       create(:piece_justificative, :contrat, type_de_piece_justificative: tpj)
@@ -31,6 +32,22 @@ describe PieceJustificativeToChampPieceJointeMigrationService do
     expect(storage_service).to receive(:make_attachment)
   end
 
+  describe '.number_of_champs_to_migrate' do
+    let!(:other_dossier) { make_dossier }
+
+    it 'reports the numbers of champs to be migrated' do
+      expect(service.number_of_champs_to_migrate(procedure)).to eq(4)
+    end
+
+    context 'when the procedure has hidden dossiers' do
+      let!(:hidden_dossier) { make_dossier(hidden: true) }
+
+      it 'reports the numbers of champs including those of hidden dossiers' do
+        expect(service.number_of_champs_to_migrate(procedure)).to eq(6)
+      end
+    end
+  end
+
   context 'when conversion succeeds' do
     context 'for the procedure' do
       it 'types de champ are created for the "pièces jointes" header and for each PJ' do
@@ -114,19 +131,26 @@ describe PieceJustificativeToChampPieceJointeMigrationService do
           .to change { dossier.pieces_justificatives.count }
           .to(0)
       end
+
+      context 'when the procedure has several dossiers' do
+        let!(:other_dossier) { make_dossier }
+
+        it 'sends progress callback for each migrated champ' do
+          number_of_champs_to_migrate = service.number_of_champs_to_migrate(procedure)
+
+          progress_count = 0
+          service.convert_procedure_pjs_to_champ_pjs(procedure) do
+            progress_count += 1
+          end
+
+          expect(progress_count).to eq(number_of_champs_to_migrate)
+        end
+      end
     end
 
     context 'when the dossier is soft-deleted it still gets converted' do
       let(:pjs) { make_pjs }
-
-      let!(:dossier) do
-        create(
-          :dossier,
-          procedure: procedure,
-          pieces_justificatives: pjs,
-          hidden_at: Time.zone.now
-        )
-      end
+      let!(:dossier) { make_dossier(hidden: true) }
 
       before { expect_storage_service_to_convert_object }