refactor proxy

Signed-off-by: Christian Richter <crichter@owncloud.com>

extensions/proxy/pkg/cs3/client.go

@@ -0,0 +1,39 @@
+package cs3
+
+import (
+	gateway "github.com/cs3org/go-cs3apis/cs3/gateway/v1beta1"
+	proxytracing "github.com/owncloud/ocis/extensions/proxy/pkg/tracing"
+	"go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/insecure"
+)
+
+func newConn(endpoint string) (*grpc.ClientConn, error) {
+	conn, err := grpc.Dial(
+		endpoint,
+		grpc.WithTransportCredentials(insecure.NewCredentials()),
+		grpc.WithUnaryInterceptor(
+			otelgrpc.UnaryClientInterceptor(
+				otelgrpc.WithTracerProvider(
+					proxytracing.TraceProvider,
+				),
+			),
+		),
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	return conn, nil
+}
+
+// GetGatewayServiceClient returns a new cs3 gateway client
+func GetGatewayServiceClient(endpoint string) (gateway.GatewayAPIClient, error) {
+	// TODO: check connection pooling
+	conn, err := newConn(endpoint)
+	if err != nil {
+		return nil, err
+	}
+
+	return gateway.NewGatewayAPIClient(conn), nil
+}