add tracing and refactor some api pkgs

internal/tracing/google/config.go

@@ -0,0 +1,25 @@
+package google
+
+import (
+	"go.opencensus.io/trace"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+
+	"github.com/caos/zitadel/internal/tracing"
+)
+
+type Config struct {
+	ProjectID    string
+	MetricPrefix string
+	Fraction     float64
+}
+
+func (c *Config) NewTracer() error {
+	if !envIsSet() {
+		return status.Error(codes.InvalidArgument, "env not properly set, GOOGLE_APPLICATION_CREDENTIALS is misconfigured or missing")
+	}
+
+	tracing.T = &Tracer{projectID: c.ProjectID, metricPrefix: c.MetricPrefix, sampler: trace.ProbabilitySampler(c.Fraction)}
+
+	return tracing.T.Start()
+}