Merge branch 'feature/PRXS-1191-MoveObserver' into 'master'

Перенесен collaborators/observer.go

See merge request perxis/perxis-go!41

pkg/collaborators/observer.go

+package collaborators
+
+import "context"
+
+type CollaboratorObserver interface{}
+
+type CollaboratorSetObserver interface {
+	OnCollaboratorSet(ctx context.Context, collaborator *Collaborator) (string, error)
+}
+
+type CollaboratorRemoveObserver interface {
+	OnCollaboratorRemove(ctx context.Context, collaborator *Collaborator) (string, error)
+}