Replace "registry" pkg with AdmissionWebhooks in SC

[adamwalach]

Description

Storage for api-server is placed in registry pkg. There we can find functions which are used to prepare for CREATE/UPDATE (mutators) and also some validators

We should be able to reuse most of the code but we will need to adjust it to fulfill webhook API.

Assumptions:

• K8s at least in version 1.9

SC

• registry package replaced using the MutatingAdmissionWebhook and ValidatingAdmissionWebhook

Blocked by: #2784

[mszostok]

For validation take into account that we have already the static validation on CRD, so recheck what else needs to be done in ValidatingAdmissionWebhook.

Check also if we shouldn't remove the static validation from CRD and implement that in ValidatingAdmissionWebhook - take into account how user-friendly is the returned validation error.

[mszostok]

Remember about DoD:

• execute make verify and it MUST end without error
• execute make test-unit and it MUST end without error
• execute make format
• check if your changes need to be applied also for svcat. If yes then modify it and then test it also manually. HINT: Create a binary:

  make svcat
  

  generated binary will be placed in bin/svcat/svcat
• finally, always generate a new image and update tag in chart
• finally, test service catalog by installing chart and walkthrough happy path flow both for namespace-scope and cluster-wide brokers. Happy path means creating and deleting all objects.

[piotrmiskiewicz]

All resources status update does executes validation.validateStatus* methods, but such methods does not performs any checks on status except ServiceBinding