Allow seting StdOut prefix (#121)

* Allow seting StdOut prefix

* Use search instead of path to unify with Kafka

Author: awegrzyn

src/Backends/StdOut.cxx

@@ -23,7 +23,7 @@ inline unsigned long StdOut::convertTimestamp(const std::chrono::time_point<std:
   ).count();
 }
 
-StdOut::StdOut() : mStream(std::cout)
+StdOut::StdOut(const std::string& prefix) : mStream(std::cout), mPrefix(prefix)
 {
   setVerbosisty(Verbosity::Debug);
   MonLogger::Get() << "StdOut backend initialized" << MonLogger::End();
@@ -54,15 +54,15 @@ void StdOut::sendMultiple(std::string measurement, std::vector<Metric>&& metrics
     metricTags += tags::GetValue(value);
   } 
   for (auto& metric : metrics) {
-    mStream << "[METRIC] " << measurement << '/' << metric.getName() << ',' << metric.getType() << ' '
+    mStream << "[" << mPrefix << "] " << measurement << '/' << metric.getName() << ',' << metric.getType() << ' '
       << metric.getValue() << ' ' << convertTimestamp(metric.getTimestamp()) << ' ' << tagString
       << metricTags << '\n';
   }
 }
 
 void StdOut::send(const Metric& metric)
 {
-  mStream << "[METRIC] " << metric.getName() << ',' << metric.getType() << " " << metric.getValue()
+  mStream << "[" << mPrefix << "] " << metric.getName() << ',' << metric.getType() << " " << metric.getValue()
           << ' ' << convertTimestamp(metric.getTimestamp()) << ' ' << tagString;
 
   for (const auto& [key, value] : metric.getTags()) {

src/Backends/StdOut.h

@@ -23,7 +23,7 @@ class StdOut final : public Backend
 {
   public:
     /// Default constructor
-    StdOut();
+    StdOut(const std::string& prefix = "METRIC");
 
     /// Default destructor
     ~StdOut() = default;
@@ -56,6 +56,7 @@ class StdOut final : public Backend
     unsigned long convertTimestamp(const std::chrono::time_point<std::chrono::system_clock>& timestamp);
 
     std::string tagString; ///< Global tagset (common for each metric)
+    const std::string mPrefix; ///< Metric prefix
 };
 
 } // namespace backends

src/MonitoringFactory.cxx

@@ -33,8 +33,12 @@ static const std::map<std::string, Verbosity> verbosities = {
   {"/debug", Verbosity::Debug}
 };
 
-std::unique_ptr<Backend> getStdOut(http::url) {
-  return std::make_unique<backends::StdOut>();
+std::unique_ptr<Backend> getStdOut(http::url uri) {
+  if (uri.search.size() > 0) {
+    return std::make_unique<backends::StdOut>(uri.search);
+  } else {
+    return std::make_unique<backends::StdOut>();
+  }
 }
 
 std::unique_ptr<Backend> getInfluxDb(http::url uri) {