Update release notes for v1 release

- Mark authentication parameter changes as breaking
- Update environment variable changes as breaking
- Add summary for v1 preparation

Signed-off-by: Mathias L. Baumann <[email protected]>

Author: Marenz

RELEASE_NOTES.md

@@ -2,11 +2,15 @@
 
 ## Summary
 
-<!-- Here goes a general summary of what this release is about -->
+Major release preparing for v1 with breaking changes to authentication parameters and dependency updates.
 
 ## Upgrading
 
-* The `key` parameter in the `Dispatcher` constructor is now deprecated. Use `auth_key` instead. The `sign_secret` parameter is an additional optional parameter for signing.
+* **BREAKING**: The `key` parameter in the `Dispatcher` constructor has been removed. Use `auth_key` instead.
+* **BREAKING**: The `sign_secret` parameter is now required for authentication.
+* **BREAKING**: Environment variables have been updated:
+  * `DISPATCH_API_KEY` → `DISPATCH_API_AUTH_KEY`
+  * `DISPATCH_API_SIGN_SECRET` is now required
 * The `components` property in `DispatchInfo` is now deprecated. Use `target` instead.
 
 ## New Features