Improve Narayana JDBC helper to create connections when needed for recovery

[gytis]

Prior this pull request, database connection were created on DataSourceXAResourceRecoveryHelper.getXAResources() call and closed on DataSourceXAResourceRecoveryHelper.recover(TMENDRSCAN) call. While this workflow is still valid for most of the time, a change in one of Narayana recovery modules, allows commit/rollback calls to appear outside of this workflow. To make sure, that those calls will get through to the database, I've introduced a ConnectionManager, which makes sure that connection is created and closed whenever needed during recovery.

[wilkinsona]

I am not keen on merging this in its current form. The Narayana auto-configuration is getting more and more complex. I'd rather remove it in 2.0 if the extra complexity is unavoidable.

[snicoll]

Agreed. Can't we move the spring boot integration back to Narayana itself? I think I'd prefer if it would be released alongside the project rather than Spring Boot.

[gytis]

@snicoll I did ask @wilkinsona if this would be possible a couple of weeks back. I agree, that it would make things easier both for us and for you to keep things simple in here and keep the complexity in Narayana side. However, as @wilkinsona said this could be problematic in 1.5 brach, because he prefers to keep it on Narayana's 5.5.x branch. Narayana is currently on 5.6.x.

[snicoll]

@gytis agreed. I was talking about Spring Boot 2 actually. This PR used to be assigned to Spring Boot 2 also...

[gytis]

Would it be doable for 1.5.x branch if I Narayana people would agree to take this logic for 5.5.x? This is just a speculation, I don't know if it's doable in their side.

[wilkinsona]

@gytis It's hard to say without knowing the exact nature of the changes. 1.5.x is our long-term maintenance branch so we need to try to avoid anything that runs the risk of destabilising things.

[gytis]

@wilkinsona assuming that configuration with starter would stay here, we would remove 8 classes from this repo and make them available via Maven dependency. It shouldn't make any difference from the user point of view.

[gytis]

Closing this PR as it seems that guys in Narayana side were able to find a fix without modifying Spring Boot side. Thanks a lot for your time!
In a future I'll still look into slimming down this integration as discussed.