feat: adding kyb schema

Author: pengying

mintlify/api-reference/sandbox-testing.mdx

@@ -10,9 +10,14 @@ import SandboxBeneficiaryVerification from '/snippets/sandbox-beneficiary-verifi
 import SandboxTransferPatterns from '/snippets/sandbox-transfer-patterns.mdx';
 import SandboxQuotePatterns from '/snippets/sandbox-quote-patterns.mdx';
 import SandboxUmaAddresses from '/snippets/sandbox-uma-addresses.mdx';
+import SandboxKybVerification from '/snippets/sandbox-kyb-verification.mdx';
 
 The Grid sandbox environment simulates real payment flows without moving real money. You can control test outcomes using special account number patterns and test addresses.
 
+## KYC/KYB verification
+
+<SandboxKybVerification />
+
 ## Adding external accounts
 
 <SandboxExternalAccounts />