chore(book): add section on key packages in the migration guide

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>

Author: typfel

CHANGELOG.md

@@ -265,7 +265,7 @@
 
   Affected platforms: all
 
-  Migration: to create key packages after initializing MLS, call `clientKeypackages()` in a transaction.
+  Migration: to create key packages after initializing MLS, call `generateKeypackage()` in a transaction.
 
 - `proteusErrorCode` field was removed from the root error type. Affected platforms: web
 

cc-book/modules/ROOT/partials/cc10-migration.adoc

@@ -22,11 +22,17 @@ endif::[]
 == MLS Initialization
 
 . `mlsInit()` was decoupled from key package creation.
-  To create key packages after initializing MLS, call `clientKeypackages()` in a transaction.
+  To create key packages after initializing MLS, call `CoreCryptoContext.generateKeypackage()` in a transaction.
 
 . removed `CoreCrypto.provideTransport()`, added `transport` parameter to `CoreCryptoContext.mlsInit()`
   Instead of providing transport separately from MLS initialization provide it when calling `mlsInit()`.
 
+== Key Packages
+
+. We *removed* `CoreCryptoContext.clientKeypackages()`. To generate a desired amount of key packages, make repeated calls to `CoreCryptoContext.generateKeypackage()`.
+
+. We *removed* `CoreCryptoContext.clientValidKeypackagesCount()`. To count remaining key packages, call `CoreCryptoContext.getKeypackages()`, and filter the results as desired, and count the remaining items.
+
 == Logging
 
 . We *removed* `CoreCrypto.setLogger(logger: CoreCryptoLogger, level: CoreCryptoLogLevel)`