allow extension defined members as only member of relationship object (json-api#1644)

jelhan · web-flow · commit 87896c8c1fc6 · 2022-07-29T14:21:25.000-04:00
diff --git a/_format/1.1/index.md b/_format/1.1/index.md
@@ -498,6 +498,7 @@ A "relationship object" **MUST** contain at least one of the following:
 * `data`: [resource linkage]
 * `meta`: a [meta object][meta] that contains non-standard meta-information about the
   relationship.
+* a member defined by an applied [extension](#extensions).
 
 A relationship object that represents a to-many relationship **MAY** also contain
 [pagination] links under the `links` member, as described below. Any
