Reduce method side effects

[mgcth]

Description

Reduce or eliminate (as much as possible) side effects from our methods. Along these lines, remove the Metobs class altogether and just use the individual components.

[docNord]

How do you think the structure should be in order to avoid such side effects, and what side effects are you thinking of?

[mgcth]

We could probably delete this class altogether

https://github.com/Ingenjorsarbete-For-Klimatet/ifk-smhi/blob/6be598b6eba0199b221f237b337887c4951e69fd/src/smhi/metobs.py#L12

For example, get_periods doesn't actually return anything, but just mutates an internal state periods of the object

https://github.com/Ingenjorsarbete-For-Klimatet/ifk-smhi/blob/6be598b6eba0199b221f237b337887c4951e69fd/src/smhi/metobs.py#L74-L93

There are probably more examples.

I think it makes the code harder to test and reason about, and as a user, I would expect get_... to return something and not only modify the object state.

I'd go for pure functions as much as possible, as long as we don't copy data unecessairly but that shouldn't be a big problem as the data here is relatively small for each request. It should simplify any future multithreading/async additions we'd want to add.

[docNord]

So... Should we pencil out a plan for how we want to structure things before we start remodeling? Or do you already have a blueprint like this in mind?

[mgcth]

Maybe we should try to release version 0.1.0 first :)

[docNord]

Good point :)