increase feemarket's consensus version and add migration handler

Closes: #1001

x/feemarket/keeper/migrations.go

@@ -1,5 +1,11 @@
 package keeper
 
+import (
+	"math/big"
+
+	sdk "github.com/cosmos/cosmos-sdk/types"
+)
+
 // Migrator is a struct for handling in-place store migrations.
 type Migrator struct {
 	keeper Keeper
@@ -11,3 +17,15 @@ func NewMigrator(keeper Keeper) Migrator {
 		keeper: keeper,
 	}
 }
+
+func (m Migrator) Migrate1to2(ctx sdk.Context) error {
+	store := ctx.KVStore(m.keeper.storeKey)
+	baseFeeKeyPrefix := []byte{2}
+	bz := store.Get(baseFeeKeyPrefix)
+	if len(bz) > 0 {
+		baseFee := new(big.Int).SetBytes(bz)
+		m.keeper.SetBaseFee(ctx, baseFee)
+	}
+	store.Delete(baseFeeKeyPrefix)
+	return nil
+}

x/feemarket/module.go

@@ -44,7 +44,7 @@ func (AppModuleBasic) RegisterLegacyAminoCodec(_ *codec.LegacyAmino) {
 
 // ConsensusVersion returns the consensus state-breaking version for the module.
 func (AppModuleBasic) ConsensusVersion() uint64 {
-	return 1
+	return 2
 }
 
 // DefaultGenesis returns default genesis state as raw bytes for the fee market
@@ -117,7 +117,11 @@ func (am AppModule) RegisterInvariants(ir sdk.InvariantRegistry) {}
 func (am AppModule) RegisterServices(cfg module.Configurator) {
 	types.RegisterQueryServer(cfg.QueryServer(), am.keeper)
 
-	_ = keeper.NewMigrator(am.keeper)
+	m := keeper.NewMigrator(am.keeper)
+	err := cfg.RegisterMigration(types.ModuleName, 1, m.Migrate1to2)
+	if err != nil {
+		panic(err)
+	}
 }
 
 // Route returns the message routing key for the fee market module.