Support Fastify route constraints

[Fcmam5]

Is there an existing issue that is already proposing this?

• I have searched the existing issues

Is your feature request related to a problem? Please describe it

I want to use Fastify's route constraints

  @RouteConstraints({
    host: 'admin.example.com',
  })

Describe the solution you'd like

Add a new RouteConstraints decorator

Teachability, documentation, adoption, migration strategy

NA

What is the motivation / use case for changing the behavior?

This would cover more of Fastify's features and enriches platform-fastify APIs

Example repository:

https://github.com/Fcmam5/fastify-route-constraints-poc

[kamilmysliwiec]

Let's track this here #12567