Update Custom Model Binding to 2.1.

[serpent5]

Addresses #16319.
Fixes #16367

[Rick-Anderson]

@serpent5 nice work, thanks!

[serpent5]

@guardrex I think this affects #5495. I'm going to look at the linked issues next and then do a 3.1 update. I dunno if you want to wait until then before updating the sample-tracker. I'm just putting it on your radar for when you're back from working through your holidays being OOF. 😄

[guardrex]

Thanks @serpent5 ... Since I'm not cross-linking to the PRs, I'll just update it in the tracking issue to 3.1 now. Well ... "now" = "Monday" 😄 lol ... I'm savoring my last two PTO days before 🏃 in January.

[serpent5]

I'm savoring my last two PTO days before 🏃 in January.

Glad to hear it. You guys work too hard but what you do is great.