[code] codacy: pass variables by reference

src/jobs.cpp

@@ -330,7 +330,7 @@ Job * Job::from_json(const std::string & json_str,
     return Job::from_json(doc, workload, error_prefix);
 }
 
-string job_state_to_string(JobState state)
+string job_state_to_string(const JobState & state)
 {
     string job_state("UNKNOWN");
 
@@ -361,7 +361,7 @@ string job_state_to_string(JobState state)
     return job_state;
 }
 
-JobState job_state_from_string(std::string state)
+JobState job_state_from_string(const std::string & state)
 {
     JobState new_state;
 

src/jobs.hpp

@@ -223,11 +223,11 @@ private:
  * @param[in] state The JobState
  * @return A std::string corresponding to a given JobState
  */
-std::string job_state_to_string(JobState state);
+std::string job_state_to_string(const JobState & state);
 
 /**
  * @brief Returns a JobState corresponding to a given std::string
  * @param[in] state The std::string
  * @return A JobState corresponding to a given std::string
  */
-JobState job_state_from_string(std::string state);
+JobState job_state_from_string(const std::string & state);