Import Model::transaction from Shopify
Add docs for Model::transaction
Move Batman.Transaction to its own file
add tests and implement TransactionAssociationSet
remove comments and leftover do
make transaction set extend Set
load empty TransactionAssociationSets for empty transactions
define .length on TransactionAssociationSet
TransactionAssociationSet tracks removed items, too
If ::transaction triggers a load on a hasMany, those items should be added to the transaction when they're loaded
add test for transaction on polymorphic has many
add test for prototype callback setup
add throw/catch test
create / throw test
implement and test association reflection
associations can opt out of transaction with includeInTransaction: false
add developer warning for mutable objects
add SetMapping, tests and docs
check for {} objects only
make implementation and docs better