Account namespace updates: part 4 (transfers, singular namespacing) (#896)

* Move Transfer to Account namespace

* Fix partial resolution due to namespacing plurality

* Make category and tag controllers consistent with namespacing convention

* Update stale partial reference

test/controllers/category/deletions_controller_test.rb

@@ -0,0 +1,40 @@
+require "test_helper"
+
+class Category::DeletionsControllerTest < ActionDispatch::IntegrationTest
+  setup do
+    sign_in users(:family_admin)
+    @category = categories(:food_and_drink)
+  end
+
+  test "new" do
+    get new_category_deletion_url(@category)
+    assert_response :success
+  end
+
+  test "create with replacement" do
+    replacement_category = categories(:income)
+
+    assert_not_empty @category.transactions
+
+    assert_difference "Category.count", -1 do
+      assert_difference "replacement_category.transactions.count", @category.transactions.count do
+        post category_deletions_url(@category),
+          params: { replacement_category_id: replacement_category.id }
+      end
+    end
+
+    assert_redirected_to transactions_url
+  end
+
+  test "create without replacement" do
+    assert_not_empty @category.transactions
+
+    assert_difference "Category.count", -1 do
+      assert_difference "Transaction.where(category: nil).count", @category.transactions.count do
+        post category_deletions_url(@category)
+      end
+    end
+
+    assert_redirected_to transactions_url
+  end
+end