Remove PerformError (#3066)

This removes `PerformError`, which was needed when we still had
polylith.

This removes quite a bunch of
```go
if err != nil {
	return err
}
if err := res.Error; err != nil {
	return err.JSONResponse()
}
```

Hopefully can be read commit by commit. [skip ci]

clientapi/routing/membership.go

@@ -20,6 +20,7 @@ import (
 	"net/http"
 	"time"
 
+	"github.com/getsentry/sentry-go"
 	"github.com/matrix-org/gomatrixserverlib"
 	"github.com/matrix-org/gomatrixserverlib/spec"
 
@@ -265,22 +266,33 @@ func sendInvite(
 		return jsonerror.InternalServerError(), err
 	}
 
-	var inviteRes api.PerformInviteResponse
-	if err := rsAPI.PerformInvite(ctx, &api.PerformInviteRequest{
+	err = rsAPI.PerformInvite(ctx, &api.PerformInviteRequest{
 		Event:           event,
 		InviteRoomState: nil, // ask the roomserver to draw up invite room state for us
 		RoomVersion:     event.Version(),
 		SendAsServer:    string(device.UserDomain()),
-	}, &inviteRes); err != nil {
+	})
+
+	switch e := err.(type) {
+	case roomserverAPI.ErrInvalidID:
+		return util.JSONResponse{
+			Code: http.StatusBadRequest,
+			JSON: jsonerror.Unknown(e.Error()),
+		}, e
+	case roomserverAPI.ErrNotAllowed:
+		return util.JSONResponse{
+			Code: http.StatusForbidden,
+			JSON: jsonerror.Forbidden(e.Error()),
+		}, e
+	case nil:
+	default:
 		util.GetLogger(ctx).WithError(err).Error("PerformInvite failed")
+		sentry.CaptureException(err)
 		return util.JSONResponse{
 			Code: http.StatusInternalServerError,
 			JSON: jsonerror.InternalServerError(),
 		}, err
 	}
-	if inviteRes.Error != nil {
-		return inviteRes.Error.JSONResponse(), inviteRes.Error
-	}
 
 	return util.JSONResponse{
 		Code: http.StatusOK,