Step Factory

[devhawk]

This PR introduces Step Factories, a special kind of step for database access. Step factory steps execute as a single transaction, committing both step changes and DBOS chceckpoint atomically

Note, in TS this is called a datasource but in Java the term DataSource is already in use

This inial step factory PR provides an abstract PostgresStepFactory plus concrete step factories for JDBC, JDBI and JOOQ. A future PR will add declarative support for Spring Boot at a minimum (a @TransactionalStep annotation to complement @Transactional)

Note, It is NOT our intention to implement a Step Factory for every ORM and query builder in the Java ecosystem. We did three common ones to prove out the model. While we include the core JDBC step factory and related infrastructure in the base transact pacakge, this could have been implemented completely independently of DBOS. Community members who wish to support step factories for other libraries and/or transactional data stores are welcome to build them, ship them independenty and/or open PRs

fixes #185

[kraftp]

I notice the name StepFactory is very broad and there's a more specific PostgresStepFactory. Do you envision using this interface for something other than transactional steps?

[devhawk]

I notice the name StepFactory is very broad and there's a more specific PostgresStepFactory. Do you envision using this interface for something other than transactional steps?

Not really. I originally was using "TransactionalStepFactory" but then thought that was just too long.

[kraftp]

Looks good! My only quibble is the name, it's not obvious what a StepFactory is. One basic alternative might be TransactionFactory, or even TransactionRunner since it's not really a factory as far as I can tell, it doesn't produce classes but rather runs transactional steps.

[devhawk]

FYI, I converted this back to draft while I work on the class structure