Add job monitor interface to allow for collecting job metrics (#659)

* Add metrics each run of job

* Fix lint

* Fix test lint

* Fix backwards job status

* Add tags

* Comment example

* Rename it

* Fix some names

* Fix readme

* update readme, examples, naming

* fix unrelated test that was leaking scheduler

* remove overzealous leak detection

* rename interface methods

---------

Co-authored-by: gorodet-sky <gorodetsky.dev@gmail.com>

executor.go

@@ -23,6 +23,7 @@ type executor struct {
 	limitMode        *limitModeConfig
 	elector          Elector
 	locker           Locker
+	monitor          Monitor
 }
 
 type jobIn struct {
@@ -350,11 +351,21 @@ func (e *executor) runJob(j internalJob, shouldSendOut bool) {
 		}
 	}
 
+	startTime := time.Now()
 	err := callJobFuncWithParams(j.function, j.parameters...)
+	if e.monitor != nil {
+		e.monitor.RecordJobTiming(startTime, time.Now(), j.id, j.name, j.tags)
+	}
 	if err != nil {
 		_ = callJobFuncWithParams(j.afterJobRunsWithError, j.id, j.name, err)
+		if e.monitor != nil {
+			e.monitor.IncrementJob(j.id, j.name, j.tags, Fail)
+		}
 	} else {
 		_ = callJobFuncWithParams(j.afterJobRuns, j.id, j.name)
+		if e.monitor != nil {
+			e.monitor.IncrementJob(j.id, j.name, j.tags, Success)
+		}
 	}
 }