Add description of how to get wallet data

ecosystem/sep-0024.md

@@ -335,6 +335,11 @@ Request Parameters:
 | `lang`                        | string                  | (optional) Defaults to `en` if not specified or if the specified language is not supported. Language code specified using [RFC 4646] which means it can also accept locale in the format `en-US`. `error` fields in the response, as well as the interactive flow UI and any other user-facing strings returned for this transaction should be in this language.                                                                 |
 | `claimable_balance_supported` | boolean                 | (optional) True if the client supports receiving deposit transactions as a claimable balance, false otherwise.                                                                                                                                                                                                                                                                                                                   |
 
+When anchor receives a request, it can determine an origin of the request. First, it should check `client_domain` value 
+of the authentication token. If it's set, this wallet is an origin of the request. Otherwise, `sub` value of the JWT 
+is the origin of the request. For custodial wallets, anchor should store internal mapping between wallet keys and wallet 
+domains. Note, that custodial wallets should only use 1 authentication key, so it's easy to map them.
+
 Additionally, any [SEP-9](sep-0009.md) parameters may be passed as well to make the onboarding experience simpler.
 
 When uploading data for fields specificed in [SEP-9](sep-0009.md), `binary` type fields (typically files) should be