Decompose Serverless webhook

[kwiatekus]

Description

Get rid of serverless webhook:

Replace validation logic with kubernetes validation rules in CRDs

• Replace validation webhook logic with the x-kubernetes-validations  #250

Move necessary defaulting to controller

• Move resource profiles defaulting from mutating webhook to function controller. #248

Drop excesive unnecessary validation

• Drop function requested resources vs limit validation from the serverless webhook #249

• Drop validation logic for Function's spec.replicas  #251

• Remove profiles for function replicas #252

Eliminate mutation of docker registry secret

• Support native dockerconfigjson secrets when configuring docker registry for serverless #121
• Delete secret mutation webhook #335

Reasons

By getting rid of our webhook we can improve resiliency of serverless module and remove the problem of CA generation.
Webhooks are intercepting calls to apiserver and introduce another point of failure.
User can apply functions CR only after webhook is up, and it takes it a while until its up.
If we get rid of webhooks we will enable true declarative way of defining function - this improves development experience for function developers.

Attachments

Succesful POC
https://kubernetes.io/docs/tasks/extend-kubernetes/custom-resources/custom-resource-definitions/#validation