feat: store migration setup (#794)

* feat: store migration setup

* comment

* changelog

x/feemarket/keeper/migrations.go

@@ -0,0 +1,13 @@
+package keeper
+
+// Migrator is a struct for handling in-place store migrations.
+type Migrator struct {
+	keeper Keeper
+}
+
+// NewMigrator returns a new Migrator.
+func NewMigrator(keeper Keeper) Migrator {
+	return Migrator{
+		keeper: keeper,
+	}
+}

x/feemarket/module.go

@@ -116,6 +116,8 @@ func (am AppModule) RegisterInvariants(ir sdk.InvariantRegistry) {}
 // module-specific GRPC queries.
 func (am AppModule) RegisterServices(cfg module.Configurator) {
 	types.RegisterQueryServer(cfg.QueryServer(), am.keeper)
+
+	_ = keeper.NewMigrator(am.keeper)
 }
 
 // Route returns the message routing key for the fee market module.