fix(AIP-136): allow complex GET as POST (#1623)

Author: noahdietz

aip/general/0136.md

@@ -51,6 +51,8 @@ services. The bullets below apply in all three cases.
     considered), a custom `CreateBookLongRunning` method could be introduced.
 - The HTTP method **must** be `GET` or `POST`:
   - `GET` **must** be used for methods retrieving data or resource state.
+    - `POST` **may** be used for data retieval methods if the request payload could
+      exceed URL size limitations, thus requiring a `body`.
   - `POST` **must** be used if the method has side effects or mutates resources
     or data.
 - The HTTP URI **must** use a `:` character followed by the custom verb
@@ -188,6 +190,7 @@ languages.
 
 ## Changelog
 
+- **2026-06-09:** Allow complex GET to be POST if necessary.
 - **2025-05-12:** Extend disallowing prepositions rationale.
 - **2025-01-09:** Add original rationale for disallowing prepositions in names.
 - **2023-11-16:** Included link to AIP-127 "HTTP and gRPC Transcoding" for guidance on body definition.