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/account/transfers_controller_test.rb

@@ -0,0 +1,33 @@
+require "test_helper"
+
+class Account::TransfersControllerTest < ActionDispatch::IntegrationTest
+  setup do
+    sign_in users(:family_admin)
+  end
+
+  test "should get new" do
+    get new_account_transfer_url
+    assert_response :success
+  end
+
+  test "can create transfers" do
+    assert_difference "Account::Transfer.count", 1 do
+      post account_transfers_url, params: {
+        account_transfer: {
+          from_account_id: accounts(:checking).id,
+          to_account_id: accounts(:savings).id,
+          date: Date.current,
+          amount: 100,
+          currency: "USD",
+          name: "Test Transfer"
+        }
+      }
+    end
+  end
+
+  test "can destroy transfer" do
+    assert_difference -> { Account::Transfer.count } => -1, -> { Transaction.count } => 0 do
+      delete account_transfer_url(account_transfers(:credit_card_payment))
+    end
+  end
+end