Add check if device name is already used

[nathanael-h]

Problem

You can overwrite an existing device configuration with a new one by reusing the same name.

Fixes #260

[nathanael-h]

This prevents adding a device with the name of an existing device.

Here is a screenshot:

I'd like to have a better error message, "This device name is already used." Can someone guide on how to add this?

Logs:

ERRO[0155]device_service.go:30 device name already taken                     grpc.method=AddDevice grpc.service=proto.Devices grpc.start_time="2022-12-22T16:35:38+01:00" span.kind=server system=grpc trace.id=c5f289eb-18c6-4a89-9ab6-f4a4987fabe8

[mergeable]

Thanks for creating a pull request! A maintainer will review your changes shortly. Please don't be discouraged if it takes a while.

[nathanael-h]

Mmmh... I think that to improve the error message, we'd need to do this:
// TODO: unwrap grpc error message
https://github.com/freifunkMUC/wg-access-server/blob/master/website/src/components/AddDevice.tsx#L70

In another PR maybe?

[DasSkelett]

Mmmh... I think that to improve the error message, we'd need to do this: // TODO: unwrap grpc error message master/website/src/components/AddDevice.tsx#L70

In another PR maybe?

This would also need changing:

wg-access-server/internal/services/device_service.go

Lines 28 to 32 in dfab842

	device, err := d.DeviceManager.AddDevice(user, req.GetName(), req.GetPublicKey())
	if err != nil {
	ctxlogrus.Extract(ctx).Error(err)
	return nil, status.Errorf(codes.Internal, "failed to add device")
	}

...but one has to be careful there, as not to leak secrets or other sensitive data through wrapped error messages.

I'm okay with postponing this to another PR, as it is a bit more involved.

[nathanael-h]

Hello, do you know when a new release with this PR would be released?