deps: update protobuf

The module we used previouly, github.com/golang/protobuf/proto, is
deprecated. See https://github.com/golang/protobuf/releases/tag/v1.5.2
and golang/protobuf#1306.

We use the official succssor:

```
(fix imports)
go get google.golang.org/protobuf/proto@v1.28.1
go mod tidy
```

The .pb.go generated files also needed to be updated with an updated
protoc-gen-go:

```
go install google.golang.org/protobuf/cmd/protoc-gen-go@v1.28.1
```

A new script was added to generate the files, as the
`import_path=messages` flag seems to be removed in favour of the `M`
flag, which unfortunately has to be specified for each .proto file :(

-----------

In `BTCSign()`, the inputs are not copied anymore due to:

```
api/firmware/btc.go:300:20: cannot use &input (value of type **messages.BTCSignInputRequest) as *messages.BTCSignInputRequest value in struct literal (typecheck)
					BtcSignInput: &input,
```

README.md

@@ -7,11 +7,15 @@ tagging versions.
 
 Clone the [BitBox02 firmware repo](https://github.com/digitalbitbox/bitbox02-firmware):
 
+Make sure you have `protoc` and
+[protoc-gen-go](https://developers.google.com/protocol-buffers/docs/reference/go-generated)
+installed:
+
 `git clone https://github.com/digitalbitbox/bitbox02-firmware.git`
 
 ```sh
-rm -rf api/firmware/messages/*
+rm -rf api/firmware/messages/{*.pb.go,*.proto}
 cp /path/to/bitbox02-firmware/messages/*.proto api/firmware/messages/
 rm api/firmware/messages/backup.proto
-go generate ./...
+./api/firmware/messages/generate.sh
 ```

api/firmware/btc.go

@@ -24,7 +24,7 @@ import (
 	"github.com/digitalbitbox/bitbox02-api-go/api/firmware/messages"
 	"github.com/digitalbitbox/bitbox02-api-go/util/errp"
 	"github.com/digitalbitbox/bitbox02-api-go/util/semver"
-	"github.com/golang/protobuf/proto"
+	"google.golang.org/protobuf/proto"
 )
 
 const multisigNameMaxLen = 30
@@ -277,7 +277,7 @@ func (device *Device) BTCSign(
 		switch next.Type {
 		case messages.BTCSignNextResponse_INPUT:
 			inputIndex := next.Index
-			input := *tx.Inputs[inputIndex].Input
+			input := tx.Inputs[inputIndex].Input
 
 			inputIsSchnorr := isTaproot(scriptConfigs[input.ScriptConfigIndex])
 
@@ -297,7 +297,7 @@ func (device *Device) BTCSign(
 			}
 			next, err = device.queryBtcSign(&messages.Request{
 				Request: &messages.Request_BtcSignInput{
-					BtcSignInput: &input,
+					BtcSignInput: input,
 				}})
 			if err != nil {
 				return nil, err

api/firmware/btc_test.go

@@ -20,8 +20,8 @@ import (
 
 	"github.com/digitalbitbox/bitbox02-api-go/api/firmware/messages"
 	"github.com/digitalbitbox/bitbox02-api-go/util/semver"
-	"github.com/golang/protobuf/proto"
 	"github.com/stretchr/testify/require"
+	"google.golang.org/protobuf/proto"
 )
 
 const hardenedKeyStart = 0x80000000

api/firmware/device.go

@@ -27,8 +27,6 @@ import (
 	"github.com/flynn/noise"
 )
 
-//go:generate sh -c "protoc --proto_path=messages/ --go_out='import_path=messages,paths=source_relative:messages' messages/*.proto"
-
 var (
 	lowestSupportedFirmwareVersion                   = semver.NewSemVer(9, 0, 0)
 	lowestSupportedFirmwareVersionBTCOnly            = semver.NewSemVer(9, 0, 0)

api/firmware/device_test.go

@@ -25,8 +25,8 @@ import (
 	"github.com/digitalbitbox/bitbox02-api-go/api/firmware/mocks"
 	"github.com/digitalbitbox/bitbox02-api-go/util/semver"
 	"github.com/flynn/noise"
-	"github.com/golang/protobuf/proto"
 	"github.com/stretchr/testify/require"
+	"google.golang.org/protobuf/proto"
 )
 
 // newDevice creates a device to test with, with init/pairing already processed.