Move away from global tracers. (#6591)

* Move away from global tracers.

This PR moves away from global tracers and instead initialises
a tracer provider at Service setup and passes it where it needs to be.

* Change tracing provider to be set via options.

Also change name for GetServiceTraceProvider.

* Add changelog.

services/proxy/pkg/config/tracing.go

@@ -1,5 +1,7 @@
 package config
 
+import "github.com/owncloud/ocis/v2/ocis-pkg/tracing"
+
 // Tracing defines the available tracing configuration.
 type Tracing struct {
 	Enabled   bool   `yaml:"enabled" env:"OCIS_TRACING_ENABLED;PROXY_TRACING_ENABLED" desc:"Activates tracing."`
@@ -7,3 +9,13 @@ type Tracing struct {
 	Endpoint  string `yaml:"endpoint" env:"OCIS_TRACING_ENDPOINT;PROXY_TRACING_ENDPOINT" desc:"The endpoint of the tracing agent."`
 	Collector string `yaml:"collector" env:"OCIS_TRACING_COLLECTOR;PROXY_TRACING_COLLECTOR" desc:"The HTTP endpoint for sending spans directly to a collector, i.e. http://jaeger-collector:14268/api/traces. Only used if the tracing endpoint is unset."`
 }
+
+// Convert Tracing to the tracing package's Config struct.
+func (t Tracing) Convert() tracing.Config {
+	return tracing.Config{
+		Enabled:   t.Enabled,
+		Type:      t.Type,
+		Endpoint:  t.Endpoint,
+		Collector: t.Collector,
+	}
+}