Investigate differences between on/off taps and ask Littlepay about them

[lauriemerrell]

As an analytics engineer, I want to understand cases where key attributes differ between on and off taps in a variable fare payments transaction so that I can handle the differences appropriately in modeling.

This is a follow up to #2663.

AC:

• [ ] Investigate specifically which fields currently differ between tap on/tap off transactions
• [ ] Ask Littlepay about the interpretation of these differences
• [ ] Write follow up tickets as needed based on responses