[FEAT] Add dive number as a var

[MOchiara]

I am not sure this has been decided as an official OG1 var but Callum is using it and we need it if we want to run a suggestion Callum has for the glider track map

[MOchiara]

I made the PR on Eleanor repo but remembered we have it here

[eleanorfrajka]

Ok - divenum exists as default in Seaglider nomenclature. What do you expect divenum to be?

For Seaglider, a divenum increments for each dive-climb cycle. (I'd have to doublecheck how the incrementing goes if the glider doesn't surface--but I'm pretty sure it still increments.) It means that I've defined OG1 "profile number" based on divenum2-1 and divenum2, so that divecycle 1 splits into profile number 1 (dive) and 2 (climb).

But also - dive_num doesn't exist in OG1, and I'm not sure I see any reason to have both dive_num and profile_number. I'm thinking we should keep glidertest as 'clean' as possible, i.e. not require variables that aren't in the official OG1 format (or, if they're needed, then generate them temporarily within glidertest), otherwise we'll end up with a side version of the official data format. This means glidertest will break for anyone who isn't using our special side-version of OG1.

[MOchiara]

Fair point! I will make a PR on glidertest where we then derive DIVE NUM from profile rather than expecting it to have it (while we wait for OG1 to officially have profile number or dive number or both)

[eleanorfrajka]

One more thing on naming. If OG1 does create it, I suspect they'll use a similar naming as for PROFILE_NUMBER, i.e., DIVE_NUMBER rather than DIVE_NUM. What do you think? Should we anticipate and call it DIVE_NUM instead? Might also eliminate questions from users--like, why is this "number" and the other is "num", and does it mean something different.