transactionManager
@Bean
@ConditionalOnMissingBean(value = [TransactionManager::class] )
An OctaviusJdbcTransactionManager, unless the context declares a TransactionManager of its own - JDBC, JPA or reactive alike, as for Boot's. Declared as the class it is, so a bean created before it can inject it by that type.
Boot's transaction manager customizers are applied to it: spring.transaction.default-timeout reaches it, and so does a TransactionManagerCustomizer<OctaviusJdbcTransactionManager> bean - the way to change its OctaviusJdbcTransactionManager.timeoutScope without declaring the manager yourself. spring.transaction.rollback-on-commit-failure reaches it too and changes nothing, as the class says.