fix(ValidationStream): Add cookie and data to interface (#2110)

Add and document more fields on the ValidationStream interface

Fixes #2095

packages/xrpl/HISTORY.md

@@ -4,7 +4,9 @@ Subscribe to [the **xrpl-announce** mailing list](https://groups.google.com/g/xr
 ## Unreleased
 ### Added
 * Support for ExpandedSignerList amendment that expands the maximum signer list to 32 entries.
+* Add `cookie` and `data` to `ValidationStream` interface
 * Addtional check for memos field format, provide more detailed error messages.
+
 ## 2.4.0 (2022-09-01)
 ### Added
 * Export `verify` from ripple-keypairs as `verifyKeypairSignature` for use in web-apps.

packages/xrpl/src/models/methods/subscribe.ts

@@ -189,6 +189,18 @@ export interface ValidationStream extends BaseStream {
   amendments?: string[]
   /** The amendments this server wants to be added to the protocol. */
   base_fee?: number
+  /**
+   * An arbitrary value chosen by the server at startup.
+   *
+   * If the same validation key pair signs validations with different cookies
+   * concurrently, that usually indicates that multiple servers are incorrectly
+   * configured to use the same validation key pair.
+   */
+  cookie?: string
+  /**
+   * The contents of the validation message in its canonical binary form
+   */
+  data?: string
   /**
    * The unscaled transaction cost (reference_fee value) this server wants to
    * set by Fee voting.