Validate escape config

[nichollsh]

Set p_xuv and z_xuv to surface when ZEPHYRUS is disabled. Closes #286 and #258

Ensure that configuration uses MORS+Spada when ZEPHYRUS is enabled. Related to #232.

Avoid spurious values for period in first iteration. Calculation of this quantity depends on M_star, which is undefined when period is first calculated, and can cause some strange behaviour. Fixed this by ensuring that M_star is always defined.

[EmmaPostolec]

Hi Harrison, very nice job ! The condition on Pxuv computation is really nice to save some computational time. Also, very nice idea to create the get_heigh_from_pressure function, very effective. Thanks for introducing error message also for the user. The computation of mu in the orbit/wrapper.py is not really linked to this issue ?

[nichollsh]

Thanks Emma! The issue with mu is something that's slightly odd. I noticed that the tests sometimes fail with MacOS, even though they succeed on my PC. I think this is because of this period parameter being set by some undefined behaviour.

[EmmaPostolec]

Also I think this PR is linked to #258 ?

[nichollsh]

Yes! It is. I didn't notice this issue, thanks Emma.

[EmmaPostolec]

No worries! I assigned myself this task but you did it faster than me :)

[lsoucasse]

I happy with these changes. You can merge them now Harrison so that I can update and merge my current PR afterwards.

[nichollsh]

Ah okay, sure! Thanks Laurent.