DOC: #38067 add missing holiday observance rules
- [x] closes #38067

Updated docs with missing functions.

`weekend_to_monday` and `next_monday` do indeed do the exact same thing, and I agree that `next_monday` should be deprecated. Any thoughts?

Thanks @dontgoto 

> weekend_to_monday and next_monday do indeed do the exact same thing, and I agree that next_monday should be deprecated. Any thoughts?

Yeah that makes sense to deprecate one of them if they are redundant 
> Yeah that makes sense to deprecate one of them if they are redundant

Can I put in a deprecation notice for 4.0.0? Or something like that?
 My two cents here - I think "weekend_to_monday" is more accurate and descriptive, BUT if that's the one we keep it would make the most sense to also change the current "previous_friday" to "weekend_to_friday".  I think it's clearest to keep the before/after and next/previous pairs as matched as possible ... so whichever gets deprecated, the pair should be either:

* weekend_to_monday and weekend_to_friday
* next_monday and previous_friday

I prefer the former but wouldn't care too much if folks prefer the latter. > * weekend_to_monday and weekend_to_friday
> 
> * next_monday and previous_friday

I find the former function names make more sense , because in the end they only shift when on a weekend, the latter implies that weekdays are also shifted, but they're not.

On the other hand, the latter ones have been in the user guide since forever, the former ones not.
 @dontgoto I agree on the "makes more sense" ... even though the others have been documented I think that can be got around by deprecating them for a while before they go away