Merge branch 'document-availability' into 'master'

Document `availability` property of user status resource

See merge request gitlab-org/gitlab!59591

doc/api/users.md

@@ -645,6 +645,7 @@ Example response:
 ```json
 {
   "emoji":"coffee",
+  "availability":"busy",
   "message":"I crave coffee :coffee:",
   "message_html": "I crave coffee <gl-emoji title=\"hot beverage\" data-name=\"coffee\" data-unicode-version=\"4.0\">☕</gl-emoji>",
   "clear_status_at": null
@@ -672,6 +673,7 @@ Example response:
 ```json
 {
   "emoji":"coffee",
+  "availability":"busy",
   "message":"I crave coffee :coffee:",
   "message_html": "I crave coffee <gl-emoji title=\"hot beverage\" data-name=\"coffee\" data-unicode-version=\"4.0\">☕</gl-emoji>",
   "clear_status_at": null