added code snippet in prefix doc

Author: Shikha Maheshwari

docs/DA-prefix.md

@@ -36,3 +36,23 @@ To ensure compatibility and consistency, the prefix must follow these rules:
 - Must **not end** with a hyphen (`-`)
 - Must **not contain consecutive hyphens** (`--`)
 - Maximum length: **16 characters**
+
+Here is the code snippet for your reference.
+
+```hcl
+validation {
+  condition = (var.prefix == null || var.prefix == "" ? true :
+    alltrue([
+      can(regex("^[a-z][-a-z0-9]*[a-z0-9]$", var.prefix)),
+      length(regexall("--", var.prefix)) == 0
+    ])
+  )
+  error_message = "Prefix must begin with a lowercase letter and may contain only lowercase letters, digits, and hyphens '-'. It must not end with a hyphen('-'), and cannot contain consecutive hyphens ('--')."
+ }
+
+  validation {
+   # must not exceed 16 characters in length
+    condition = length(var.prefix) <= 16
+    error_message = "Prefix must not exceed 16 characters."
+ }
+```