docs: gateway: changelog entry for new changes

CHANGELOG.md

@@ -17,6 +17,10 @@
 - https://github.com/filecoin-project/lotus/pull/12292: feat: p2p: allow overriding bootstrap nodes with environmemnt variable
 - https://github.com/filecoin-project/lotus/pull/12319: feat: `lotus send CLI`: allow sending to ETH addresses
 
+## ☢️ Upgrade Warnings ☢️
+
+- lotus-gateway behaviour, CLI arguments and APIs have received minor changes. See the improvements section below.
+
 ## New features
 
 - feat: Add trace filter API supporting RPC method `trace_filter` ([filecoin-project/lotus#12123](https://github.com/filecoin-project/lotus/pull/12123)). Configuring `EthTraceFilterMaxResults` sets a limit on how many results are returned in any individual `trace_filter` RPC API call.
@@ -25,10 +29,15 @@
 
 ## Improvements
 
-- fix!: gateway: fix rate limiting, general cleanup ([filecoin-project/lotus#12315](https://github.com/filecoin-project/lotus/pull/12315)).
+- feat!: gateway: fix rate limiting, better stateful handling ([filecoin-project/lotus#12315](https://github.com/filecoin-project/lotus/pull/12315)).
   - CLI usage documentation has been improved for `lotus-gateway`
   - `--per-conn-rate-limit` now works as advertised.
+  - `--eth-max-filters-per-conn` is new and allows you to set the maximum number of filters and subscription per connection, it defaults to 16.
+    - Previously, this limit was set to `16` and applied separately to filters and subscriptions. This limit is now unified and applies to both filters and subscriptions.
+  - Stateful Ethereum APIs (those involving filters and subscriptions) are now disabled for plain HTTP connections. A client must be using websockets to access these APIs.
+    - These APIs are also now automatically removed from the node by the gateway when a client disconnects.
   - Some APIs have changed which may impact users consuming Lotus Gateway code as a library.
+  - The default value for the `Events.FilterTTL` config option has been reduced from 24h to 1h. This means that filters will expire on a Lotus node after 1 hour of not being accessed by the client.
 
 # v1.28.1 / 2024-07-24