feat(CCDB): add getForRunMiddleTimeStamp method

Adds a new method `getForRunMiddleTimeStamp` to the `CCDBManagerInstance`
class. This method retrieves an object of type `T` from the CCDB using the
path and the middle timestamp of the given run number. This is a useful
utility method for cases where the exact timestamp does not matter and the
run number is available.

CCDB/include/CCDB/BasicCCDBManager.h

@@ -102,6 +102,10 @@ class CCDBManagerInstance
   template <typename T>
   T* getForTimeStamp(std::string const& path, long timestamp);
 
+  /// retrieve an object of type T from CCDB as stored under path and using the timestamp in the middle of the run
+  template <typename T>
+  T* getForRunMiddleTimeStamp(std::string const& path, int runNumber);
+
   /// retrieve an object of type T from CCDB as stored under path, timestamp and metaData
   template <typename T>
   T* getSpecific(std::string const& path, long timestamp = -1, MD metaData = MD())
@@ -311,6 +315,20 @@ T* CCDBManagerInstance::getForTimeStamp(std::string const& path, long timestamp)
   return ptr;
 }
 
+template <typename T>
+T* CCDBManagerInstance::getForRunMiddleTimeStamp(std::string const& path, int runNumber)
+{
+  auto [start, stop] = getRunDuration(runNumber);
+  if (start < 0 || stop < 0) {
+    if (mFatalWhenNull) {
+      reportFatal(std::string("Failed to get run duration for run ") + std::to_string(runNumber));
+    }
+    return nullptr;
+  }
+  return getForTimeStamp<T>(path, start / 2 + stop / 2);
+}
+
+
 class BasicCCDBManager : public CCDBManagerInstance
 {
  public: