feat: initial enforcement of template policy

backend/src/services/certificate-template/certificate-template-validators.ts

@@ -0,0 +1,14 @@
+import safe from "safe-regex";
+import z from "zod";
+
+export const validateTemplateRegexField = z
+  .string()
+  .min(1)
+  .max(100)
+  .regex(/^[a-zA-Z0-9 *@\-\\.\\]+$/, {
+    message: "Invalid pattern: only alphanumeric characters, spaces, *, ., @, -, and \\ are allowed."
+  })
+  // we ensure that the inputted pattern is computationally safe by limiting star height to 1
+  .refine((v) => safe(v), {
+    message: "Unsafe REGEX pattern"
+  });