Transaction pooling

[jesperpedersen]

Create a pipeline that pools connections on the transaction boundary.

The slot will be valid during the start() method of the pipeline. The user / database information should be copied to a pipeline memory segment.

If pgagroal_get_connection() returns a non-zero value an error should be sent to the client and communication terminated.

Implementation should be in pipeline_transaction.c.

Configuration should be done through

[pgagroal]

pipeline = transaction