Use DB for auth sessions (#1233)

* DB sessions

* Validations for profile image

test/controllers/registrations_controller_test.rb

@@ -24,14 +24,6 @@ class RegistrationsControllerTest < ActionDispatch::IntegrationTest
     end
   end
 
-  test "sets last_login_at on successful registration" do
-    post registration_url, params: { user: {
-      email: "john@example.com",
-      password: "password",
-      password_confirmation: "password" } }
-    assert_not_nil User.find_by(email: "john@example.com").last_login_at
-  end
-
   test "create when hosted requires an invite code" do
     with_env_overrides REQUIRE_INVITE_CODE: "true" do
       assert_no_difference "User.count" do