C2MS11 — Re-evaluate Optional Boolean Fields

Some message fields of type Boolean are listed as optional. This has a pretty ambiguous meaning for a boolean, which if present, is always True or False.

For one non-exhaustive example, some messages include a FINAL-MESSAGE boolean field that is optional. What does it mean when not present? It could be inferred that it is equivalent to False, but it could also be inferred that this is ignored when there is only one message, which would be the same as True.

We need to go through all these usages individually and decide if these should be required, rather than optional.