wip: add api method to check if tracer is enabled

Author: psx95

api/include/opentelemetry/trace/noop.h

@@ -108,6 +108,10 @@ class OPENTELEMETRY_EXPORT NoopTracer final : public Tracer,
     return noop_span;
   }
 
+  bool IsEnabled() const noexcept override {
+    return false;
+  }
+
 #if OPENTELEMETRY_ABI_VERSION_NO == 1
 
   void ForceFlushWithMicroseconds(uint64_t /*timeout*/) noexcept override {}

api/include/opentelemetry/trace/tracer.h

@@ -137,6 +137,13 @@ class Tracer
         options);
   }
 
+  /**
+   * Returns a boolean indicating if the tracer is enabled or not. Disabled tracers behave like
+   * no-op tracers. By default, tracers are considered enabled.
+   * @return true if the tracer is enabled, false otherwise.
+   */
+   virtual bool IsEnabled() const noexcept = 0;
+
   /**
    * Set the active span. The span will remain active until the returned Scope
    * object is destroyed.

sdk/include/opentelemetry/sdk/trace/tracer.h

@@ -96,6 +96,10 @@ class Tracer final : public opentelemetry::trace::Tracer,
     return GetInstrumentationScope();
   }
 
+  bool IsEnabled() const noexcept override {
+    return tracer_config_->IsEnabled();
+  }
+
   /** Returns the currently configured resource **/
   const opentelemetry::sdk::resource::Resource &GetResource() { return context_->GetResource(); }