x/ibc: implement 09-localhost per specification (#5769)

Signed-off-by: Gregory Hill <gregorydhill@outlook.com>

x/ibc/02-client/exported/exported.go

@@ -142,6 +142,7 @@ type ClientType byte
 // available client types
 const (
 	Tendermint ClientType = iota + 1 // 1
+	Localhost
 )
 
 // string representation of the client types

x/ibc/02-client/handler.go

@@ -8,6 +8,7 @@ import (
 	"github.com/cosmos/cosmos-sdk/x/ibc/02-client/exported"
 	"github.com/cosmos/cosmos-sdk/x/ibc/02-client/types"
 	ibctmtypes "github.com/cosmos/cosmos-sdk/x/ibc/07-tendermint/types"
+	localhost "github.com/cosmos/cosmos-sdk/x/ibc/09-localhost"
 )
 
 // HandleMsgCreateClient defines the sdk.Handler for MsgCreateClient
@@ -27,6 +28,8 @@ func HandleMsgCreateClient(ctx sdk.Context, k Keeper, msg exported.MsgCreateClie
 		if err != nil {
 			return nil, err
 		}
+	case exported.Localhost:
+		clientState = localhost.NewClientState(ctx.MultiStore().GetKVStore(k.GetStoreKey()))
 	default:
 		return nil, sdkerrors.Wrap(ErrInvalidClientType, msg.GetClientType())
 	}

x/ibc/02-client/keeper/keeper.go

@@ -40,6 +40,10 @@ func (k Keeper) Logger(ctx sdk.Context) log.Logger {
 	return ctx.Logger().With("module", fmt.Sprintf("x/%s/%s", ibctypes.ModuleName, types.SubModuleName))
 }
 
+func (k Keeper) GetStoreKey() sdk.StoreKey {
+	return k.storeKey
+}
+
 // GetClientState gets a particular client from the store
 func (k Keeper) GetClientState(ctx sdk.Context, clientID string) (exported.ClientState, bool) {
 	store := k.clientStore(ctx, clientID)