Fix join codes skipping user setup

If someone joined an account with the same identity as they were signed in with the old logic would skip the user setup step

test/controllers/join_codes_controller_test.rb

@@ -43,6 +43,9 @@ class JoinCodesControllerTest < ActionDispatch::IntegrationTest
     identity = identities(:jz)
     sign_in_as :jz
 
+    assert identity.member_of?(@account), "JZ should be a member of 37s for this test"
+    assert identity.users.find_by!(account: @account).setup?, "JZ's user should be setup for this test"
+
     assert_no_difference -> { Identity.count } do
       assert_no_difference -> { User.count } do
         post join_path(code: @join_code.code, script_name: @account.slug), params: { email_address: identity.email_address }
@@ -51,4 +54,19 @@ class JoinCodesControllerTest < ActionDispatch::IntegrationTest
 
     assert_redirected_to landing_url(script_name: @account.slug)
   end
+
+  test "create for signed-in identity without a user in the account redirects to user setup" do
+    identity = identities(:mike)
+    sign_in_as :mike
+
+    assert_not identity.member_of?(@account), "Mike should not be a member of 37s for this test"
+
+    assert_no_difference -> { Identity.count } do
+      assert_difference -> { User.count }, 1 do
+        post join_path(code: @join_code.code, script_name: @account.slug), params: { email_address: identity.email_address }
+      end
+    end
+
+    assert_redirected_to new_users_join_url(script_name: @account.slug)
+  end
 end