FDW API / flow charts for the docs?

Hi,

I've been experimenting with the new reworked FDW API to get familiar
with it. The postgres_fdw is a great source of knowledge (huge thanks to
Shigeru Hanada, KaiGai Kohei and everyone else who made this happen),
but in the end I had to draw some flow charts in Dia, to understand how
exactly do the functions interact, pass private data etc. in various
scenarios.

Attached is the set of flow charts, showing the sequence of callbacks
for all the supported commands (i.e. SELECT, INSERT, UPDATE, DELETE,
ANALYZE). Wouldn't it be useful to put something like this into the
docs? I mean, the FDW API is not going to get any simpler, and for me
this was a significant help.

regards
Tomas