chore: restore pending dkg contract state migration (#6116)

since it has not yet been run on mainnet

Author: jstuczyn

contracts/coconut-dkg/src/contract.rs

@@ -255,10 +255,12 @@ pub fn query(deps: Deps<'_>, env: Env, msg: QueryMsg) -> Result<QueryResponse, C
 }
 
 #[entry_point]
-pub fn migrate(deps: DepsMut<'_>, _env: Env, _msg: MigrateMsg) -> Result<Response, ContractError> {
+pub fn migrate(deps: DepsMut<'_>, env: Env, _msg: MigrateMsg) -> Result<Response, ContractError> {
     set_build_information!(deps.storage)?;
     cw2::ensure_from_older_version(deps.storage, CONTRACT_NAME, CONTRACT_VERSION)?;
 
+    crate::queued_migrations::introduce_historical_epochs(deps, env)?;
+
     Ok(Response::new())
 }
 

contracts/coconut-dkg/src/queued_migrations.rs

@@ -1,2 +1,21 @@
 // Copyright 2025 - Nym Technologies SA <[email protected]>
 // SPDX-License-Identifier: Apache-2.0
+
+use crate::epoch_state::storage::HISTORICAL_EPOCH;
+use crate::error::ContractError;
+use cosmwasm_std::{DepsMut, Env};
+
+pub fn introduce_historical_epochs(deps: DepsMut, env: Env) -> Result<(), ContractError> {
+    if HISTORICAL_EPOCH.may_load(deps.storage)?.is_some() {
+        return Err(ContractError::FailedMigration {
+            comment: "this migration has already been run before".to_string(),
+        });
+    }
+
+    #[allow(deprecated)]
+    let current = crate::epoch_state::storage::CURRENT_EPOCH.load(deps.storage)?;
+    // we won't have information on intermediate states prior to now, but that's not the end of the world
+    HISTORICAL_EPOCH.save(deps.storage, &current, env.block.height)?;
+
+    Ok(())
+}