Add data normalization and validation. Add validation error error type.

Add lookup by code method to pis class.

src/lib/errors.ts

@@ -14,4 +14,11 @@ export class ApiError extends Error {
         // cast fallback to ensure it satisfies union
         this.code = errorObj.code || ("SERVER" as ApiErrorCode);
     }
+}
+
+export class ValidationError extends Error {
+    constructor(public field: string, public reason: string) {
+        super(`validation failed for ${field}: ${reason}`);
+        this.name = "VALIDATIONERROR";
+    }
 }