add upgrade docs for mitmproxy 7

docs/src/content/addons-api-changelog.md

@@ -0,0 +1,46 @@
+---
+title: "API Changelog"
+layout: single
+menu:
+    addons:
+        weight: 9
+---
+
+# API Changelog
+
+We try to avoid them, but this page lists breaking changes in the mitmproxy addon API.
+
+## mitmproxy 7.0
+
+#### Connection Events
+
+We've revised mitmproxy's connection-specific event hooks as part of the new proxy core. See the new 
+[event hook documentation]({{< relref "addons-api#ConnectionEvents" >}}) for details. As the passed objects are slightly
+different now, we've also taken this opportunity to introduce a consistent event names:
+
+| mitmproxy 6 | mitmproxy 7 |
+|--|--|
+| `clientconnect` | `client_connected` |
+| `clientdisconnect` | `client_disconnected` |
+| ❌ | `server_connect` |
+| `serverconnect` | `server_connected` |
+| `serverdisconnect` | `server_disconnected` |
+
+#### Logging
+
+The `log` event has been renamed to `add_log`. This fixes a consistent source of errors where users imported 
+modules with the name "log", which were then inadvertedly picked up.
+
+#### Contentviews
+
+Contentviews now implement `render_priority` instead of `should_render`. This enables additional specialization, for
+example one can now write contentviews that pretty-print only specific JSON responses.
+See the [contentview.py]({{< relref "addons-examples#contentview" >}}) example for details.
+
+#### WebSocket Flows
+
+mitmproxy 6 had a custom WebSocketFlow class, which had 
+[ugly co-dependencies with the related HTTPFlow](https://github.com/mitmproxy/mitmproxy/issues/4425). Long story short,
+WebSocketFlow is no more and instead HTTPFlow has a neat 
+[`.websocket` attribute]({{< relref "api/mitmproxy.http.md#HTTPFlow.websocket" >}}). All WebSocket flows are now passed
+the originating `HTTPFlow` with this attribute set.