Address review: add eviction_strategy input validation

- Add (String) type hint to the comment to clarify quoting is required
- Add note that unquoted None becomes null under JINJA2_NATIVE=true
- Create validations/kubevirt_vm.yml to assert the variable is a valid
  string and one of 'None' or 'LiveMigrate' before module execution

Author: aisa-b

roles/sap_vm_provision/defaults/main.yml

@@ -822,7 +822,7 @@ sap_vm_provision_kubevirt_vm_os_user_password: ""
 # RAM Overhead [GiB] for virt-launcher container, this can be small for VMs < 1 TB and without SRIOV but should be increased to 16 or more for VMs > 1TB
 sap_vm_provision_kubevirt_vm_container_memory_overhead: 1
 
-# Eviction strategy for KubeVirt VMs.
+# Eviction strategy for KubeVirt VMs (String).
 # Set to 'None' for local storage (ReadWriteOnce PVCs) or 'LiveMigrate' for shared storage (ReadWriteMany).
 sap_vm_provision_kubevirt_vm_eviction_strategy: "None"
 

roles/sap_vm_provision/tasks/validations/kubevirt_vm.yml

@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: Apache-2.0
+---
+
+- name: Assert that the variable 'sap_vm_provision_kubevirt_vm_eviction_strategy' is defined as valid string
+  ansible.builtin.assert:
+    that:
+      - sap_vm_provision_kubevirt_vm_eviction_strategy is defined
+      - sap_vm_provision_kubevirt_vm_eviction_strategy is string
+      - sap_vm_provision_kubevirt_vm_eviction_strategy in ['None', 'LiveMigrate']
+    fail_msg: |
+      The variable 'sap_vm_provision_kubevirt_vm_eviction_strategy' is undefined or invalid.
+      It should be one of: 'None' for local storage (ReadWriteOnce PVCs) or 'LiveMigrate' for shared storage (ReadWriteMany).