Use PublicProject validations in PublicProject:Update

We can re-use the validations in the `PublicProject` wrapper class to
ensure that, in `Api::PublicProjectsController#update`, the project
identifier is updated to a non-blank value in the correct format and the
project name is updated to a non-blank value.

lib/concepts/public_project/operations/update.rb

@@ -7,9 +7,10 @@ def call(project:, update_hash:)
         response = OperationResponse.new
 
         project.assign_attributes(update_hash)
-        project.save!
+        public_project = PublicProject.new(project)
+        public_project.save!
 
-        response[:project] = project
+        response[:project] = public_project.project
         response
       rescue StandardError => e
         Sentry.capture_exception(e)

spec/concepts/public_project/update_spec.rb

@@ -43,5 +43,41 @@
         expect(Sentry).to have_received(:capture_exception).with(kind_of(StandardError))
       end
     end
+
+    context 'when identifier is blank' do
+      let(:new_identifier) { nil }
+
+      it 'returns failure' do
+        expect(update_project.failure?).to be(true)
+      end
+
+      it 'returns error message' do
+        expect(update_project[:error]).to eq("Error updating project: Validation failed: Identifier can't be blank")
+      end
+    end
+
+    context 'when identifier is in invalid format' do
+      let(:new_identifier) { 'FooBarBaz' }
+
+      it 'returns failure' do
+        expect(update_project.failure?).to be(true)
+      end
+
+      it 'returns error message' do
+        expect(update_project[:error]).to eq('Error updating project: Validation failed: Identifier is invalid')
+      end
+    end
+
+    context 'when name is blank' do
+      let(:new_name) { '' }
+
+      it 'returns failure' do
+        expect(update_project.failure?).to be(true)
+      end
+
+      it 'returns error message' do
+        expect(update_project[:error]).to eq("Error updating project: Validation failed: Name can't be blank")
+      end
+    end
   end
 end

spec/features/public_project/updating_a_public_project_spec.rb

@@ -84,4 +84,9 @@
     put('/api/public_projects/another-identifier?project_type=scratch', headers:, params:)
     expect(response).to have_http_status(:not_found)
   end
+
+  it 'responds 422 Unprocessable Entity when params are invalid' do
+    put("/api/public_projects/#{project.identifier}?project_type=scratch", headers:, params: { project: { name: '' } })
+    expect(response).to have_http_status(:unprocessable_entity)
+  end
 end