docs: bump version and update changelog/ADR for openedx#369

Every merged PR in this repo bumps __version__ and adds a CHANGELOG.rst
entry (feat -> minor bump, per semver); this PR was missing both.

Also update the "extending Scope" section of the architecture ADR
(0005), which still described the old per-subclass
get_or_create_for_external_key() contract instead of the current
LINKED_OBJECT_FIELD/external_key_for_object() one.

Author: efortish

CHANGELOG.rst

@@ -14,13 +14,14 @@ Change Log
 Unreleased
 **********
 
-1.21.2 - 2026-07-29
+1.22.0 - 2026-07-30
 *******************
 
-Fixed
+Added
 =====
 
-* Exclude superadmin entries from the user-specific assignments endpoint following the same pattern as the global assignments endpoint.
+* Role assignment now succeeds for a course/library scope key before its CourseOverview/ContentLibrary
+  exists, and links up automatically once the object is created. (#369)
 
 1.21.1 - 2026-07-24
 *******************

openedx_authz/__init__.py

@@ -4,6 +4,6 @@
 
 import os
 
-__version__ = "1.21.2"
+__version__ = "1.22.0"
 
 ROOT_DIRECTORY = os.path.dirname(os.path.abspath(__file__))