Add transaction support to Immugw

**What would you like to be added or enhanced**
Hi!
I would like to have the ability to run multiple queries and/or sqlexecs within a single ImmuDB transaction using Immugw. As I understand and as @jeroiraz confirmed, Immugw ability to use session-based authentication (openSession/closeSession) is missing.

**Why is this needed**
This feature is needed in order to support multiple changes, queries, and/or requests withing a single transaction, e.g. the ability to effectively commit or rollback the transaction.

**Additional context**
At this moment there is a hack to put multiple SQL requests into single sqlexec but that is suboptimal.

Start by reviewing Immugw's existing sqlexec handling and the openSession/closeSession behavior mentioned in the issue. Define how multiple queries or sqlexecs share one transaction and how commit or rollback is exposed; done means session-based authentication supports those operations within a single transaction.

Written by the indexing model from the issue text.