docs: adding a section on the 10 minute signing window restriction (#944)

* docs: adding a section on the 10 minute signing window restriction for canton coin

adding a section on the 10 minute signing window restriction for canton coin

Signed-off-by: davidrichards-da <[email protected]>

* Making updates based on Phillip's feedback

Signed-off-by: davidrichards-da <[email protected]>

* Resolving the 'WARNING: Duplicate explicit target name: "here"' error

Signed-off-by: davidrichards-da <[email protected]>

---------

Signed-off-by: davidrichards-da <[email protected]>

Author: davidrichards-da

docs/wallet-integration-guide/src/canton-coin-specific-considerations/index.rst

@@ -0,0 +1,66 @@
+Canton Coin Specific Considerations
+===================================
+
+Handling Time-Bound Signatures (Canton Coin)
+--------------------------------------------
+
+If your wallet infrastructure relies on offline signing, cold storage, or multi-party approval flows that take longer than **10–20 minutes**, then this guide is for you.
+
+The 10-Minute Signing Window
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Canton Coin transactions operate on a strict **10-minute minting cycle**. Unlike standard Daml transactions, 
+**Canton Coin** transfers and acceptances must reference a specific 
+`OpenMiningRound <https://docs.dev.sync.global/app_dev/api/splice-amulet/Splice-Round.html>`_ contract to 
+calculate network fees and rewards.
+
+* A new ``OpenMiningRound`` is created every **10 minutes**.
+* The contract remains active for approximately **20 minutes** (the current round + overlap).
+* **The Problem:** If you prepare a transaction referencing *Round A*, but you do not sign and submit it before *Round A* expires, the network will reject it.
+
+**Common Error:**
+If your transaction exceeds this window, the API will return a ``409 Conflict`` with the following error:
+
+.. code-block:: text
+
+   LOCAL_VERDICT_INACTIVE_CONTRACTS
+
+There is one way of handle incoming transfers and another way to handle outgoing transfers, listed below.
+
+Solution 1: Implement Pre-approvals for Incoming Transfers / Receiving Funds
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+**Use Case:** Your users need to receive Canton Coin, but you cannot sign a transaction within 10 minutes 
+(e.g., due to cold storage of the receiver's keys).
+
+**The Fix:** Enable **1-Step Transfers** using `Pre-approvals <https://docs.digitalasset.com/integrate/devnet/token-standard/index.html#step-transfer-vs-1-step-transfer>`_.
+
+Instead of signing every incoming transfer, the receiver signs a single, long-living ``TransferPreapproval`` 
+contract. This authorizes the sending party (or a specific provider) to deposit funds immediately without 
+requiring an interactive acceptance signature for every transaction.
+
+To do this, create a `Splice.Wallet.TransferPreapproval` contract. The guide on how to create the pre-approval 
+contract in the `Wallet SDK is here <https://docs.digitalasset.com/integrate/devnet/token-standard/index.html#step-transfer-vs-1-step-transfer>`_ 
+and the general information about `Canton Coin Preapprovals is here <https://docs.dev.sync.global/background/preapprovals.html>`_. 
+By implementing a preapproval contract the receiver doesn't need to accept Canton Coin transfers sent to 
+them as they are automatically accepted.
+
+Solution 2: Use Command Delegation for Outgoing Transfers / Sending Funds 
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+**Use Case:** Your users need to send Canton Coin, but the signing process (e.g., institutional custody approval) takes hours.
+
+**The Fix:** Use **Command Delegation** - `TransferCommand <https://docs.dev.sync.global/app_dev/api/splice-amulet/Splice-ExternalPartyAmuletRules.html>`_.
+
+Instead of signing the transfer transaction directly (which pins a short-lived Mining Round), the user signs a long-living instruction to transfer funds.
+
+How it works
+""""""""""""
+
+1.  **User Signs Instruction:** The user signs a transaction to create a ``Splice.ExternalPartyAmuletRules.TransferCommand`` contract.
+    
+    * This contract **does not** reference a mining round.
+    * It can remain valid for up to 24 hours (or as defined by ``expiresAt``).
+
+2.  **Delegated Execution:** Once this command is on the ledger, a Super Validator (SV) or a delegate picks it up.
+
+3.  **Execution:** The delegate executes the actual transfer. The *delegate* selects the current ``OpenMiningRound`` at the moment of execution, ensuring the transaction succeeds regardless of how long ago the user signed the instruction.

docs/wallet-integration-guide/src/index.rst

@@ -25,6 +25,7 @@ It's suggested that the Wallet SDK is used to simplify the majority of workflows
    traffic/index
    tokenomics-and-rewards/index
    user-management/index
+   canton-coin-specific-considerations/index
    deposits-into-exchanges/index
    exchange-integration/index
    release-notes/index