Improve documentation and add more tests

internal/repository/jobHooks.go

@@ -10,8 +10,36 @@ import (
 	"github.com/ClusterCockpit/cc-lib/v2/schema"
 )
 
+// JobHook interface allows external components to hook into job lifecycle events.
+// Implementations can perform actions when jobs start or stop, such as tagging,
+// logging, notifications, or triggering external workflows.
+//
+// Example implementation:
+//
+//	type MyJobTagger struct{}
+//
+//	func (t *MyJobTagger) JobStartCallback(job *schema.Job) {
+//	    if job.NumNodes > 100 {
+//	        // Tag large jobs automatically
+//	    }
+//	}
+//
+//	func (t *MyJobTagger) JobStopCallback(job *schema.Job) {
+//	    if job.State == schema.JobStateFailed {
+//	        // Log or alert on failed jobs
+//	    }
+//	}
+//
+// Register hooks during application initialization:
+//
+//	repository.RegisterJobHook(&MyJobTagger{})
 type JobHook interface {
+	// JobStartCallback is invoked when one or more jobs start.
+	// This is called synchronously, so implementations should be fast.
 	JobStartCallback(job *schema.Job)
+
+	// JobStopCallback is invoked when a job completes.
+	// This is called synchronously, so implementations should be fast.
 	JobStopCallback(job *schema.Job)
 }
 
@@ -20,7 +48,13 @@ var (
 	hooks    []JobHook
 )
 
-func RegisterJobJook(hook JobHook) {
+// RegisterJobHook registers a JobHook to receive job lifecycle callbacks.
+// Multiple hooks can be registered and will be called in registration order.
+// This function is safe to call multiple times and is typically called during
+// application initialization.
+//
+// Nil hooks are silently ignored to simplify conditional registration.
+func RegisterJobHook(hook JobHook) {
 	initOnce.Do(func() {
 		hooks = make([]JobHook, 0)
 	})
@@ -30,6 +64,12 @@ func RegisterJobJook(hook JobHook) {
 	}
 }
 
+// CallJobStartHooks invokes all registered JobHook.JobStartCallback methods
+// for each job in the provided slice. This is called internally by the repository
+// when jobs are started (e.g., via StartJob or batch job imports).
+//
+// Hooks are called synchronously in registration order. If a hook panics,
+// the panic will propagate to the caller.
 func CallJobStartHooks(jobs []*schema.Job) {
 	if hooks == nil {
 		return
@@ -44,6 +84,12 @@ func CallJobStartHooks(jobs []*schema.Job) {
 	}
 }
 
+// CallJobStopHooks invokes all registered JobHook.JobStopCallback methods
+// for the provided job. This is called internally by the repository when a
+// job completes (e.g., via StopJob or job state updates).
+//
+// Hooks are called synchronously in registration order. If a hook panics,
+// the panic will propagate to the caller.
 func CallJobStopHooks(job *schema.Job) {
 	if hooks == nil {
 		return