Add order-preserving requirement for resource name patterns

Fixes b/356396132

Author: jskeet

aip/general/0123.md

@@ -78,6 +78,10 @@ message Topic {
 - Pattern variables **must** be unique within any given pattern. (e.g.
   `projects/{abc}/topics/{abc}` is invalid; this is usually a natural
   corollary of collection identifiers being unique within a pattern.)
+- Resources with [multiple patterns][aip-4231#multi-pattern-resources]) **must**
+  preserve ordering: new patterns **must** be added at the end of the list, and
+  existing patterns **must not** be removed or re-ordered, as this breaks client
+  library backward compatibility.
 - Singular **must** be the lower camel case of the type.
   - Pattern variables **must** be the singular form of the resource type e.g.
     a pattern variable representing a `Topic` resource ID is named `{topic}`.
@@ -110,6 +114,7 @@ such as UpperCamelCase and snake_case.
 
 <!-- prettier-ignore-start -->
 [aip-122]: ./0122.md
+[aip-4231]: ./4231.md
 [API Group]: https://kubernetes.io/docs/concepts/overview/kubernetes-api/#api-groups
 [nested collections]: ./0122.md#collection-identifiers
 [Object]: https://github.com/kubernetes/community/blob/master/contributors/devel/sig-architecture/api-conventions.md#types-kinds
@@ -119,9 +124,10 @@ such as UpperCamelCase and snake_case.
 
 ## Changelog
 
-- **2023-09-19**: Prohibit duplicate pattern variables.
-- **2023-05-06**: Adding requirement of singular and plural.
-- **2023-01-28**: Clarifying guidance for the resource type name.
+- **2024-08-07**: Added multi-pattern ordering compatibility requirements.
+- **2023-09-19**: Prohibited duplicate pattern variables.
+- **2023-05-06**: Added requirement of singular and plural.
+- **2023-01-28**: Clarified guidance for the resource type name.
 - **2022-10-28**: Added pattern variable format guidance.
 - **2020-05-14**: Added pattern uniqueness.
 - **2019-12-05**: Added guidance on patterns.

aip/general/0180.md

@@ -243,9 +243,11 @@ version.
 - For compatibility with client library resource name parsing, see [AIP-4231][]
 - For compatibility with client library method signatures, see [AIP-4232][]
 - For compatibility around field presence changes, see [AIP-149][].
+- For compatibility around resource types, see [AIP-123][].
 
 ## Changelog
 
+- **2024-08-07**: Added reference to resource type compatibility.
 - **2024-06-05**: Added reference to field presence compatibility.
 - **2023-07-26**: Added reference to field behavior compatibility.
 - **2023-07-26**: Added note on APIs which have limited clients.
@@ -256,6 +258,7 @@ version.
 
 <!-- prettier-ignore-start -->
 [aip-122]: ./0122.md
+[aip-123]: ./0123.md
 [aip-149]: ./0149.md
 [aip-151]: ./0151.md
 [aip-158]: ./0158.md