[keycloak-dev] jta, emf, db migration

[Bill Burke]

Currently there is some issues with master since I added JTA 
transactions to the mix

* KeycloakDS datasource config now requires jta=false.  This breaks 
backward compatibility and has migration issues.  This was done because 
both RESOURCE_LOCAL EntityManagers and Liquibase (using raw JDBC) cannot 
function within a JTA transaction.

* Our EntityManager implementation is not controlled by JTA. This is not 
great as the db connection cannot be involved with XA, especially if 
another external transaction resource  is involved when doing events 
and/or user federation.

To do this I had to do some things that may be a little weird.

* Entity Manager is now JTA managed if JTA exists in the environment 
keycloak is running in.  The side effect of this is that all 
interactions with the EntityManager need to happen within a JTA 
transaction (or you get an exception).
* jta=false is reverted in server distribution
* All DBLock and Liquibase operations now suspend any existing JTA 
transaction before executing.  You cannot call commit/rollback on a JDBC 
connection if you are getting a connection from a JTA aware db 
connection pool and there is a JTA connection active.  DBLock calls a 
rollback() for some reason...if running in JTA, this marks the 
connection as rolled back and you can't use the connection after that.  
So basically for DBLock and Liquibase there's a lot of issues with 
running inside a JTA transaction.

Honestly, this code can and should be refactored into different 
providers (i.e. a DBMigrationProvider), but I've got so many other 
things I need to refactor right now I'm going to put this on the back 
burner.

Bill