I can set the value mapper and function provider in the builder

[saig0]

Description

The DMN engine uses a value mapper and a function provider to build the internal FEEL engine. Currently, the value mapper and the function provider are loaded via Java's SPI.

We should extend the builder to pass the value mapper and the function provider directly (without using Java's SPI mechanism).

[saig0]

@korthout this is a potential issue for you to make the first steps in this project 🚀