add empty migrate (#505)

add empty migrate msg

## 1. Overview

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## 2. Implementation details

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rationale. -->

## 3. How to test/use

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## 4. Checklist

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- [ ] Does the Readme need to be updated?

## 5. Limitations (optional)

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section. -->

## 6. Future Work (optional)

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smart-contracts/contracts/cl-vault/src/contract.rs

@@ -2,7 +2,7 @@ use crate::error::{ContractError, ContractResult};
 use crate::instantiate::{
     handle_create_denom_reply, handle_instantiate, handle_instantiate_create_position_reply,
 };
-use crate::msg::{ExecuteMsg, InstantiateMsg, ModifyRangeMsg, QueryMsg};
+use crate::msg::{ExecuteMsg, InstantiateMsg, ModifyRangeMsg, QueryMsg, MigrateMsg};
 use crate::query::{
     query_info, query_metadata, query_pool, query_position, query_total_assets,
     query_total_vault_token_supply, query_user_balance, query_user_rewards,
@@ -150,5 +150,10 @@ pub fn reply(deps: DepsMut, env: Env, msg: Reply) -> Result<Response, ContractEr
     }
 }
 
+#[entry_point]
+pub fn migrate(_deps: DepsMut, _env: Env, _msg: MigrateMsg) -> Result<Response, ContractError> {
+    Ok(Response::new().add_attribute("migrate", "successful"))
+}
+
 #[cfg(test)]
 mod tests {}