For AI Search add Knowledge Source and Knowledge Base as azapi_data_plane_resource

The two new features Knowledge Source (https://learn.microsoft.com/en-us/azure/search/agentic-knowledge-source-overview) and Knowledge Base (https://learn.microsoft.com/en-us/azure/search/agentic-retrieval-how-to-create-knowledge-base?tabs=rbac%2C2026-05-01-preview&pivots=python) in Azure AI Search are currently not configurable via azapi in terraform, it would be awesome to add those two.

Could relate to: https://github.com/Azure/terraform-provider-azapi/pull/1146

Read the linked Azure AI Search documentation for Knowledge Source and Knowledge Base, then inspect the existing azapi_data_plane_resource entry point and related PR #1146. Compare how current data-plane resources are exposed through Terraform and confirm that both new Azure AI Search features can be configured through azapi.

Written by the indexing model from the issue text.