docs: Update migration guide

.github/MIGRATION.md

@@ -229,6 +229,10 @@ Namely, the node/API it is sent to will "broadcast" the transaction to the mempo
 
 ### `serialize` methods
 
+Most users shouldn't need to use `serializeXyz` methods.
+Concepts in Stacks.js have helpers like `postConditionToHex` instead.
+Serialization is meant for internal representations in transactions, mostly not for user-facing data.
+
 Existing methods now take or return **hex-encoded strings** _instead_ of `Uint8Array`s.
 
 > If you were already converting returned bytes to hex-strings in your code, you can now skip the conversion step — hex-strings are the new default.

packages/transactions/src/wire/serialization.ts

@@ -673,6 +673,7 @@ export function serializeTransactionAuthFieldBytes(field: TransactionAuthFieldWi
 export function serializePublicKey(key: PublicKeyWire): string {
   return bytesToHex(serializePublicKeyBytes(key));
 }
+
 /** @ignore */
 export function serializePublicKeyBytes(key: PublicKeyWire): Uint8Array {
   return key.data.slice();