Progress: Wrap up initial pass of fl_fss_payload_header_map().

Progress: Wrap up initial pass of fl_fss_payload_header_map().

Everything for the fl_fss_payload_header_map() function is written.
I can guarantee that there is some logic error or mistake somewhere due to the codestorming practice that I did with this (in addition to doing it across multiple weeks).

I experimented with different approaches in the different private functions.
I will eventually follow up this with a clean up pass that add functions to reduce the redundant code and also standardize the logic implementations where reasonable.

My next task in regards to this function will be to write unit tests.
This will find the problems and I will use the unit tests to kick off the rewrite of the private functions.