Merge branch 'resource-label-events-api-link' into 'master'

Link to resource label events API

See merge request gitlab-org/gitlab-ce!27412

doc/api/discussions.md

@@ -2,6 +2,8 @@
 
 Discussions are set of related notes on snippets, issues, merge requests or commits.
 
+This includes system notes, which are notes about changes to the object (for example, when a milestone changes, there will be a corresponding system note). Label notes are not part of this API, but recorded as separate events in [resource label events](resource_label_events.md).
+
 ## Discussions pagination
 
 By default, `GET` requests return 20 results at a time because the API results

doc/api/notes.md

@@ -2,6 +2,8 @@
 
 Notes are comments on snippets, issues or merge requests.
 
+This includes system notes, which are notes about changes to the object (for example, when a milestone changes, there will be a corresponding system note). Label notes are not part of this API, but recorded as separate events in [resource label events](resource_label_events.md).
+
 ## Notes pagination
 
 By default, `GET` requests return 20 results at a time because the API results