Add GetTx gRPC endpoint (cosmos#7688)

* Add empty TxByHash

* Fix search & replace

* Renname to GetTx

* Make getTx grpc work

* Hash as string

* Add todo comment

* /tx

* Make tests pass

* Put into function

* Add changelog

* Fix lint

* RegisterTxService in server

* Remove comment

* Update proto/cosmos/tx/v1beta1/service.proto

Co-authored-by: Cory <cjlevinson@gmail.com>

* Create new protoCdc

* Move tx service to x/auth

* Small tweaks

* Link gh issue

* Fix lint

* Update x/auth/tx/service.go

Co-authored-by: Aleksandr Bezobchuk <alexanderbez@users.noreply.github.com>

Co-authored-by: Cory <cjlevinson@gmail.com>
Co-authored-by: Federico Kunze <31522760+fedekunze@users.noreply.github.com>
Co-authored-by: Aleksandr Bezobchuk <alexanderbez@users.noreply.github.com>
Co-authored-by: SaReN <sahithnarahari@gmail.com>

app.go

@@ -22,6 +22,7 @@ import (
 	"github.com/cosmos/cosmos-sdk/codec/types"
 	"github.com/cosmos/cosmos-sdk/server/api"
 	"github.com/cosmos/cosmos-sdk/server/config"
+	servertypes "github.com/cosmos/cosmos-sdk/server/types"
 	simappparams "github.com/cosmos/cosmos-sdk/simapp/params"
 	"github.com/cosmos/cosmos-sdk/testutil/testdata"
 	sdk "github.com/cosmos/cosmos-sdk/types"
@@ -32,6 +33,7 @@ import (
 	authrest "github.com/cosmos/cosmos-sdk/x/auth/client/rest"
 	authkeeper "github.com/cosmos/cosmos-sdk/x/auth/keeper"
 	authsims "github.com/cosmos/cosmos-sdk/x/auth/simulation"
+	authtx "github.com/cosmos/cosmos-sdk/x/auth/tx"
 	authtypes "github.com/cosmos/cosmos-sdk/x/auth/types"
 	"github.com/cosmos/cosmos-sdk/x/auth/vesting"
 	"github.com/cosmos/cosmos-sdk/x/bank"
@@ -134,7 +136,10 @@ var (
 	}
 )
 
-var _ App = (*SimApp)(nil)
+var (
+	_ App                     = (*SimApp)(nil)
+	_ servertypes.Application = (*SimApp)(nil)
+)
 
 // SimApp extends an ABCI application, but with most of its parameters exported.
 // They are exported for convenience in creating helper functions, as object
@@ -204,7 +209,6 @@ func NewSimApp(
 	bApp.SetCommitMultiStoreTracer(traceStore)
 	bApp.SetAppVersion(version.Version)
 	bApp.SetInterfaceRegistry(interfaceRegistry)
-	bApp.GRPCQueryRouter().RegisterSimulateService(bApp.Simulate, interfaceRegistry)
 
 	keys := sdk.NewKVStoreKeys(
 		authtypes.StoreKey, banktypes.StoreKey, stakingtypes.StoreKey,
@@ -544,17 +548,26 @@ func (app *SimApp) SimulationManager() *module.SimulationManager {
 func (app *SimApp) RegisterAPIRoutes(apiSvr *api.Server, apiConfig config.APIConfig) {
 	clientCtx := apiSvr.ClientCtx
 	rpc.RegisterRoutes(clientCtx, apiSvr.Router)
+	// Register legacy tx routes.
 	authrest.RegisterTxRoutes(clientCtx, apiSvr.Router)
+	// Register new tx routes from grpc-gateway.
+	authtx.RegisterGRPCGatewayRoutes(clientCtx, apiSvr.GRPCRouter)
 
+	// Register legacy and grpc-gateway routes for all modules.
 	ModuleBasics.RegisterRESTRoutes(clientCtx, apiSvr.Router)
-	ModuleBasics.RegisterGRPCGatewayRoutes(apiSvr.ClientCtx, apiSvr.GRPCRouter)
+	ModuleBasics.RegisterGRPCGatewayRoutes(clientCtx, apiSvr.GRPCRouter)
 
 	// register swagger API from root so that other applications can override easily
 	if apiConfig.Swagger {
 		RegisterSwaggerAPI(clientCtx, apiSvr.Router)
 	}
 }
 
+// RegisterTxService implements the Application.RegisterTxService method.
+func (app *SimApp) RegisterTxService(clientCtx client.Context) {
+	authtx.RegisterTxService(app.BaseApp.GRPCQueryRouter(), clientCtx, app.BaseApp.Simulate, app.interfaceRegistry)
+}
+
 // RegisterSwaggerAPI registers swagger route with API Server
 func RegisterSwaggerAPI(ctx client.Context, rtr *mux.Router) {
 	statikFS, err := fs.New()