Allow adding Image meta data (EXIF)

[Alex-developer]

Discussed in AllskyTeam/allsky#3814

^{Originally posted by stevedee August 16, 2024}
Although the text overlay module is super useful, I like to capture 'clean' images, free of clutter, once the system has been properly setup.
So wondered if you could implement the addition of image EXIF data.

I notice in the c++ file: capture_RPi.cpp some notes to implement this:-

/* TODO: what exif fields should we use?
if (myModeMeanSetting.meanAuto != MEAN_AUTO_OFF) {
stringstream strExposureTime;
stringstream strReinforcement;
strExposureTime << myRaspistillSetting.shutter_us;
strReinforcement << myRaspistillSetting.analoggain;

	command += " --exif IFD0.Artist=li_" + strExposureTime.str() + "_" + strReinforcement.str();
}

*/

I'd suggest as a minimum:-
exposure: number (ms)
gain: number
auto exposure: yes/no
auto gain: yes/no

Nice-to-have:-
author: text
camera: text
lens: text
camera temperature: 'C
focus metric: number
longitude:
latitude:

Many thanks!

[EricClaeys]

This should be done via an optional module that works for ZWO and RPi cameras.
The module could have a list of data that could be added and let the user decide. Possibly the same list as in the Variable Manager?

The hardest thing may be to determine what EXIF field names to use...