fix!: add missing gov v5 migration section

app/upgrades/v21/upgrades.go

@@ -8,6 +8,7 @@ import (
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	"github.com/cosmos/cosmos-sdk/types/module"
 
+	govkeeper "github.com/cosmos/cosmos-sdk/x/gov/keeper"
 	"github.com/cosmos/gaia/v21/app/keepers"
 )
 
@@ -29,3 +30,10 @@ func CreateUpgradeHandler(
 		return vm, nil
 	}
 }
+
+// setting the default constitution for the chain
+// this is in line with cosmos-sdk v5 gov migration: https://github.com/cosmos/cosmos-sdk/blob/v0.50.10/x/gov/migrations/v5/store.go#L57
+func InitializeConstitutionCollection(ctx sdk.Context, govKeeper govkeeper.Keeper) error {
+	govKeeper.Constitution.Set(ctx, "This chain has no constitution.")
+	return nil
+}

app/upgrades/v21/upgrades_test.go

@@ -0,0 +1,25 @@
+package v21_test
+
+import (
+	"testing"
+
+	tmproto "github.com/cometbft/cometbft/proto/tendermint/types"
+	"github.com/cosmos/gaia/v21/app/helpers"
+	v21 "github.com/cosmos/gaia/v21/app/upgrades/v21"
+	"github.com/stretchr/testify/require"
+)
+
+func TestInitializeConstitutionCollection(t *testing.T) {
+	gaiaApp := helpers.Setup(t)
+	ctx := gaiaApp.NewUncachedContext(true, tmproto.Header{})
+
+	govKeeper := gaiaApp.GovKeeper
+
+	pre, err := govKeeper.Constitution.Get(ctx)
+	require.NoError(t, err)
+	require.Equal(t, "", pre)
+	v21.InitializeConstitutionCollection(ctx, *govKeeper)
+	post, err := govKeeper.Constitution.Get(ctx)
+	require.NoError(t, err)
+	require.Equal(t, "This chain has no constitution.", post)
+}