spring-modulith-events-jpa: Option to configure which TransactionManager that the JPA repository/registry should use

[jhberges]

In scenarios with multiple datasources and transaction managers it would be nice to be able to set a specific TransactionManager instance and not rely on the default, in cases where other components also relies on the default one but expects it to be from a different datasource.

Something akin to what you might do with your own repos:

@EnableJpaRepositories(
   entityManagerFactoryRef = "forModulith",
   transactionManagerRef = "txmForModulith"
)