Resolve "Improve the event system by adding an extra Event for gNMI-Subscribe to replace the currently used Update Event"

Description

Related Issue

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

Related to #327

controller/event/event.go

@@ -19,6 +19,9 @@ const (
 
 	// TypeDelete is a delete event.
 	TypeDelete = "delete"
+
+	// TypeSusbcribe is a gNMI subscribe event.
+	TypeSubscribe = "subscribe"
 )
 
 // NewAddEvent creates a new add event.
@@ -48,12 +51,12 @@ func NewUpdateEvent(entityID uuid.UUID) Event {
 	}
 }
 
-// NewMneUpdateEvent creates a new update event for managed network elements.
-func NewMneUpdateEvent(entityID uuid.UUID, pathsAndValues map[string]string) Event {
+// NewGnmiSubscribeEvent creates a new gNMI subscribe event for managed network elements.
+func NewGnmiSubscribeEvent(entityID uuid.UUID, pathsAndValues map[string]string) Event {
 	return Event{
 		ID:                uuid.New(),
 		EntityID:          entityID,
-		Type:              TypeUpdate,
+		Type:              TypeSubscribe,
 		PathsAndValuesMap: pathsAndValues,
 	}
 }