Notes Integration - Define API + Webhook Validations

[JoseSzycho]

Define the Kubernetes API + Webhook Validations

Summary
Define the CRD fields, general API structure, and webhook validation rules needed to support a notes feature on Contact/User resource.

Deliverables

• CRD schema updates
• Webhook validation logic
• Test coverage

[JoseSzycho]

Graphql layer is ready. Waiting for https://github.com/datum-cloud/infra/pull/1191 to be approved in order to test the API on staging, and the graphql layer with it.