Use collection relation for links to collection (#404)

* Use collection relation for links to collection

* Update ogcapi-features/README.md

Co-authored-by: Phil Varner <[email protected]>

* Document that the parent and collection relations comes from STAC Item

---------

Co-authored-by: Phil Varner <[email protected]>

Author: tschaub

CHANGELOG.md

@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Added extension field to all OpenAPI specifications `x-conformance-classes` indicating the
   conformance classes they define.
 - STAC API - Item Search now requires a `root` link relation in the response from `/search`
+- Added a `collection` link from and Item to its Collection to conform with the STAC spec.
 
 ### Fixed
 

ogcapi-features/README.md

@@ -162,12 +162,11 @@ The following Link relations must exist in the Item object returned from the `/c
 | **rel**  | **href**                                     | **Media Type**       | **From**            | **Description**                                     |
 | -------- | -------------------------------------------- | -------------------- | ------------------- | --------------------------------------------------- |
 | `root`   | `/`                                          | application/json     | STAC API - Features | The root URI                                        |
-| `parent` | `/collections/{collectionId}`                | application/json     | OAFeat              | Parent reference, usually the containing Collection |
+| `collection` | `/collections/{collectionId}`            | application/json     | STAC Item           | The containing Collection |
+| `parent` | `/collections/{collectionId}`                | application/json     | STAC Item           | Parent reference, usually the containing Collection |
 | `self`   | `/collections/{collectionId}/items/{itemId}` | application/geo+json | OAFeat              | Self reference                                      |
 
-Note that the `parent` link for an Item should point to the containing Collection
-(e.g., `/collections/{collectionId}`), rather than the API sub-path
-of `/collections/{collectionId}/items/`.
+The `parent` link for an Item may point to a Collection or a Catalog.  The `collection` link for an Item will always point to the containing Collection.  Links to a Collection must point to the `/collections/{collectionId}` endpoint, rather than the API sub-path of `/collections/{collectionId}/items/`.
 
 ## Endpoints