3.12.0 release notes updates

(cherry picked from commit 23ded92)

Author: michaelklishin

release-notes/3.12.0.md

@@ -8,7 +8,7 @@ This release includes several new features and optimizations and graduates (make
 
 The user-facing areas that have seen the biggest improvements in this release are
 
- * Lower MQTT and Web MQTT memory footprint per connection
+ * Significantly [reduced MQTT and Web MQTT memory footprint per connection](https://blog.rabbitmq.com/posts/2023/03/native-mqtt/)
  * Reduced quorum queue memory footprint, improved throughput stability under load
  * Classic queue message store memory efficiency and footprint predictability
  * OAuth 2, OIDC, IDP support
@@ -223,7 +223,7 @@ This release includes all bug fixes shipped in the `3.11.x` series.
 
 #### Enhancements
 
- * Significant (up to more than 90% with some workloads) reduction in memory footprint of MQTT connections,
+ * Significant (up to more than 90% with some workloads) [reduction in memory footprint of MQTT connections](https://blog.rabbitmq.com/posts/2023/03/native-mqtt/),
    and a double digit % reduction in memory footprint of MQTT-over-WebSockets (Web MQTT) connections.
 
    GitHub issues: [#5895](https://github.com/rabbitmq/rabbitmq-server/pull/5895), [#7091](https://github.com/rabbitmq/rabbitmq-server/pull/7091), [#7234](https://github.com/rabbitmq/rabbitmq-server/pull/7234)
@@ -240,6 +240,14 @@ This release includes all bug fixes shipped in the `3.11.x` series.
    GitHub issues: [#6015](https://github.com/rabbitmq/rabbitmq-server/pull/6015), [#6201](https://github.com/rabbitmq/rabbitmq-server/pull/6201),
    [#6247](https://github.com/rabbitmq/rabbitmq-server/pull/6247)
 
+#### Bug Fixes
+
+ * Default queue type key used when add a virtual host via the HTTP API has changed from
+   `defaultqueuetype` to `default_queue_type`. `default_queue_type` will be supported
+   for a period of time for backwards compatibility.
+
+   GitHub issue: [#7738](https://github.com/rabbitmq/rabbitmq-server/pull/7738)
+
 
 ### Consul Peer Discovery Plugin