Hi, as a vendor I need to implement code that switches behavior based on the incoming GPP strings. To test my parser's correctness, I wanted to build some sample GPP strings. It turns out on the website https://iabgpp.com, constraints among the checkboxes appear overly complex (i.e. if you want to flip this bit, you must also flip other bits), making the encoder hard to work with.

For example, if I want to have a string that flips the USCA section's SaleOptOut bit to 1, I wish only that bit flipped to 1, but the constraints require other USCA bits also need to be flipped, obscuring the point. Further, the error messages are not as informative/actionable as it could be, making it hard to build a GPP string for testing purposes.

Therefore, I propose three options:

1. Remove the constraints among the checkboxes. Allow users to encode any combination of bits they'd like -- including the combinations that are not correct. This can also make the decode+encode operations on the website invertible.
2. If constraints are violated, instead of issuing an error and preventing encoding, still proceed to encode the string but issue an warning.
3. Make the error messages more informative & actionable.

My preference is 1 = 2 > 3.

Thank you!