add comprehensive documentation (#9537)

docs/misc/cloud-init.func/CLOUD_INIT_FUNC_FUNCTIONS_REFERENCE.md

@@ -0,0 +1,30 @@
+# cloud-init.func Functions Reference
+
+Cloud-init and VM provisioning functions.
+
+## Core Functions
+
+### generate_cloud_init()
+Generate cloud-init configuration.
+
+### generate_user_data()
+Generate user-data script for VM.
+
+### apply_cloud_init()
+Apply cloud-init to VM.
+
+### setup_ssh_keys()
+Deploy SSH public keys.
+
+### setup_static_ip()
+Configure static IP on VM.
+
+### setup_dns()
+Configure DNS for VM.
+
+### setup_ipv6()
+Enable IPv6 on VM.
+
+---
+
+**Last Updated**: December 2025