Prerequisites

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Issue

While looking at the onListen hook PR, I realized it is not that strict on how the application hooks refer to the instance.

• onRoute has the reference to the instance in the this parameter
• onRegister has the reference to the instance in the instance parameter
• onClose has the reference to the instance in the instance parameter
• onReady has the reference to the instance in the this reference
• onListen has the reference to the instance in the this parameter
• preClose has the reference to the instance in the this reference

I dont see any pattern.

### Tasks
- [ ] https://github.com/fastify/fastify/pull/4972
- [ ] Document the this context more clearly for every hook

How to implement it:

We choose to convert the parameters into an object and bind the this context too:

#4967 (comment)