Document using function-patch-and-transform

[negz]

What's Missing?

I'd like to start gently encouraging folks to use http://github.com/crossplane-contrib/function-patch-and-transform rather than "native" P&T. Some time after v1.15 I'd like us to consider deprecating native P&T per crossplane/crossplane#4746.

There's several pages in the docs that cover Composition that we could update, including:

https://docs.crossplane.io/master/concepts/compositions/
https://docs.crossplane.io/master/concepts/patch-and-transform/
https://docs.crossplane.io/master/getting-started/provider-aws-part-2/
https://docs.crossplane.io/master/getting-started/provider-azure-part-2/
https://docs.crossplane.io/master/getting-started/provider-gcp-part-2/

[negz]

Part of me is eager to draw people's attention to the new feature and wants to update every example of P&T to have a function-patch-and-transform equivalent (maybe in a tab). That feels like something we should consider when Functions are GA, though. For now I think it would be a good candidate to update the "Composition Functions" entry on the Compositions concepts page.

[jbw976]

Ha, I found this one just after opening #791. The new issue is a bit more aggressive and focused on functions in general, as opposed to this older issue focusing on function-patch-and-transform. Perhaps this one can be closed and we rally around #791?