XIP-21: On-chain transaction reference content type (#39)

* first pass transaction ref ct

* xip-21 in review

XIPs/xip-21-transaction-reference-content-type.md

@@ -0,0 +1,89 @@
+---
+title: On-chain transaction reference content type
+description: Provides an on-chain transaction hash or ID sent as a message.
+author: @rygine (Ry Racherbaumer), @lourou (Louis Rouffineau), @nmalzieu (Noé Malzieu), @galligan (Matt Galligan), @nakajima (Pat Nakajima), @yash-luna (Yash Lunagaria)
+discussions-to: https://community.xmtp.org/t/xip-21-on-chain-transaction-reference-content-type/532
+status: Review
+type: Standards Track
+category: XRC
+created: 2024-01-26
+---
+
+## Abstract
+
+This content type provides a reference to an on-chain transaction, such as a transaction hash or ID, sent as a message, thereby providing a direct link to on-chain activities.
+
+## Motivation
+
+The goal of the transaction reference content type is to provide transaction details in a message, facilitating the sharing of on-chain activities, such as token transfers, between users.
+
+## Specification
+
+### Content type
+
+```json
+{
+  authorityId: "xmtp.org",
+  typeId: "transactionReference",
+  versionMajor: 1,
+  versionMinor: 0,
+}
+```
+
+### Transaction reference schema
+
+```ts
+type TransactionReference = {
+  /**
+   * The namespace for the networkId
+   */
+  namespace?: string;
+  /**
+   * The networkId for the transaction, in decimal or hexidecimal format
+   */
+  networkId: number | string;
+  /**
+   * The transaction hash
+   */
+  reference: string;
+  /**
+   * Optional metadata object
+   */
+  metadata?: {
+    transactionType: string;
+    currency: string;
+    amount: number;
+    decimals: number;
+    fromAddress: string;
+    toAddress: string;
+  };
+};
+```
+
+## Rationale
+
+The `networkId` provides details of the network used for the transaction, while the `reference` field contains the hash of the transaction on the network. These two fields should be enough to display a basic reference to the transaction. An optional `namespace` field can be used for a more human-readable description of the network.
+
+In addition, optional `metadata` can be added to provide more details and a richer display of the transaction.
+
+## Backward Compatibility
+
+To maintain backward compatibility, a content fallback is stored in the codec as text — ensuring that the intent of the transaction reference content type is conveyed even in non-supporting clients.
+
+## Test Cases
+
+Test cases will validate the interpretation of schema type and effective use of a content fallback. These are essential for ensuring interoperability across XMTP platforms.
+
+## Reference Implementation
+
+You can find a reference implementation of this transaction reference content type in the [xmtp-js-content-types](https://github.com/xmtp/xmtp-js-content-types) repo under the [packages/content-type-transaction-reference](https://github.com/xmtp/xmtp-js-content-types/tree/main/packages/content-type-transaction-reference) directory.
+
+## Security Considerations
+
+While there are no known negative security implications in the data of the on-chain transaction reference content type, clients could pass inaccurate or misleading values for these fields. In addition, clients could display inaccurate or misleading values for these fields and/or link to unrelated transactions.
+
+All transactions should be confirmed on their respective blockchain.
+
+## Copyright
+
+Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/).