squash!: Added comment on legacy role mapping for clarity

Author: rodmgwgu

openedx_authz/constants/roles.py

@@ -181,6 +181,8 @@
 COURSE_BETA_TESTER = RoleData(external_key="course_beta_tester", permissions=COURSE_BETA_TESTER_PERMISSIONS)
 
 # Map of legacy course role names to their equivalent new roles
+# This mapping must be unique in both directions, since it may be used as a reverse lookup (value → key).
+# If multiple keys share the same value, it will lead to collisions.
 LEGACY_COURSE_ROLE_EQUIVALENCES = {
     "instructor": COURSE_ADMIN.external_key,
     "staff": COURSE_STAFF.external_key,