Add openEO processes version #517 (#549)

* Add openEO processes version #517

* Update openapi.yaml

* Update openapi.yaml

Co-authored-by: Stefaan Lippens <soxofaan@users.noreply.github.com>

* Update openapi.yaml

---------

Co-authored-by: Stefaan Lippens <soxofaan@users.noreply.github.com>

Author: m-mohr

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - **New extensions:**
   - [Remote Process Definition Extension](./extensions/remote-process-definition/README.md)
+- Added `version` property to `GET /processes` [#517](https://github.com/Open-EO/openeo-api/issues/517)
 
 ### Fixed
 

openapi.yaml

@@ -615,7 +615,7 @@ paths:
                   api_version:
                     type: string
                     description: >-
-                      Version number of the openEO specification this back-end
+                      Version number of the openEO API specification this back-end
                       implements.
                     enum:
                       - 1.2.0
@@ -1660,6 +1660,17 @@ paths:
                   - processes
                   - links
                 properties:
+                  version:
+                    type: string
+                    nullable: true
+                    description: >-
+                      Version number of the openEO process specification this back-end
+                      targets.
+                      If not provided or `null`, the version is either unknown or multiple versions are implemented.
+                      Clients must be able to handle multiple process specification versions at the same time.
+                      
+                      This is **not** the openEO API specification version.
+                    example: 1.2.0
                   processes:
                     type: array
                     items: