Update changelog with change details

Author: thecoop

Diff for: docs/changelog/90529.yaml

@@ -1,13 +1,24 @@
 pr: 90529
 summary: Output a consistent format when generating error json
 area: Infra/REST API
-type: "breaking, bug"
+type: bug
 issues:
  - 89387
 breaking:
-  title: Output a consistent format when generating error json
-  area: Infra/REST API
-  details: Please describe the details of this change for the release notes. You can
-    use asciidoc.
-  impact: Please describe the impact of this change to users
+  title: >-
+    Error JSON structure has changed when detailed errors are disabled
+  area: REST API
+  details: |-
+    This change modifies the JSON format of error messages returned to REST clients
+    when detailed messages are turned off.
+    Previously, JSON returned when an exception occurred, and `http.detailed_errors.enabled: false` was set,
+    just consisted of a single `"error"` text field with some basic information.
+    Setting `http.detailed_errors.enabled: true` (the default) changed this field
+    to an object with more detailed information.
+    With this change, non-detailed errors now have the same structure as detailed errors. `"error"` will now always
+    be an object with, at a minimum, a `"type"` and `"reason"` field. Additional fields are included when detailed
+    errors are enabled.
+  impact: >-
+    If you have set `http.detailed_errors.enabled: false` (the default is `true`) the structure of JSON
+    when any exceptions occur now matches the structure when detailed errors are enabled.
   notable: false