Enable passing in the raw bytes of a PKCS#12 bundle when constructing a client certificate authorizer

[manicminer]

• Also, add a simple MSI authentication stub server for testing outside Azure

Example usage

// pfxData contains a PKCS#12 bundle (.pfx file contents)
auth, err := auth.NewClientCertificateAuthorizer(ctx, environments.Global, auth.MsGraph, auth.TokenVersion2, tenantId, clientId, pfxData, "", pfxPassword)

Suggestion: base64 encode the bundle for storage in CI systems

var pfxData []byte
if cert := os.Getenv("CLIENT_CERTIFICATE"); cert != "" {
	out := make([]byte, base64.StdEncoding.DecodedLen(len(cert)))
	n, err := base64.StdEncoding.Decode(out, []byte(cert))
	if err != nil {
		// handle err
	}
	pfxData = out[:n]
}

auth, err := auth.NewClientCertificateAuthorizer(ctx, environments.Global, auth.MsGraph, auth.TokenVersion2, tenantId, clientId, pfxData, "", pfxPassword)

Using NewAuthorizer()

config := &auth.Config{
	Environment:            environments.Global,
	Version:                auth.TokenVersion2,
	TenantID:               tenantId,
	ClientID:               clientId,
	ClientCertData:         pfxData,
	ClientCertPassword:     pfxPassword,
	ClientSecret:           clientSecret,
	EnableClientCertAuth:   true,
	EnableClientSecretAuth: true,
}

authorizer, err = config.NewAuthorizer(ctx, auth.MsGraph)
if err != nil {
	// handle err
}