VendorCA from SecurityArtifacts not added to ClientCAs pool in [server.go](http://_vscodecontentref_/0) v0.6.1

[khrasool]

Problem
The bootz server v0.6.1 fails to validate client IDevID certificates during TLS handshake because the [VendorCA]certificate from SecurityArtifacts is never added to the [ClientCAs] pool.

Current Behavior

In [server.go] lines 117-119:

// In a real scenario, this cert pool would contain CA(s) that
// signed the device's IDevID cert.
vendorIDevIDPool := x509.NewCertPool()

The [vendorIDevIDPool] is created empty and never populated, even though [SecurityArtifacts.VendorCA] is available defined in [types.go].

Later at line 133, this empty pool is used:

ClientAuth: tls.VerifyClientCertIfGiven,
ClientCAs: vendorIDevIDPool,

Impact

Unary gRPC calls (GetBootstrapData, ReportStatus) that require IDevID cert validation fail with:
rpc error: code = Unavailable desc = connection error: desc = "error reading server preface: remote error: tls: unknown certificate authority"

Devices cannot bootstrap using Cisco SUDI certificates or other vendor-signed IDevID certs

Expected Behavior

The [VendorCA] should be added to the cert pool:

vendorIDevIDPool := x509.NewCertPool()
if sa.VendorCA != nil {
vendorIDevIDPool.AddCert(sa.VendorCA)
}

Environment

bootz version: v0.6.1
Platform: Cisco IOS-XR with ECC256 SUDI certificates
TLS version: 1.3

Reproduction

Configure bootz server with SecurityArtifacts containing a valid [VendorCA]
Device attempts unary RPC call with IDevID cert in TLS handshake
Server rejects with "unknown certificate authority"