Porter.Multi

[Qqwy]

This PR adds the Porter.Multi module that allows using requests with specialized response types.

Note that I've had to split off some functionality to a Porter.Internals module to prevent dependency cycles. I am not very happy that these things are theoretically visible to the user (The Porter.Internals module has to expose them for the other two modules to use it). If you know a way to improve this, that would be nice.

EDIT: I now know that as long as you do not add a module to the exposed-modules of the package information, it will not be visible outside the package. So this is not a problem at all! 😄

• Porter.Multi basic functionality of specialized return types
• Porter.Multi.andThen chaining
• Porter.Multi.map, map2, map3
• Making sure old Porter setup is enough to use the new library (adding a new type variant to Porter.Msg and a new clause to the update function to match).
• Altering the casing of variable names (which is the method I use) to dromedarisCase (which is what Porter, i.e. @peterszerzo uses).
• A Porter.Multi.fromSimple call that turns a normal Porter.Request into a Porter.Multi.Request
• example code that uses Porter.Multi

[Qqwy]

I've added a call that turns a normal Porter request into a Porter.Multi request, for compatibility's sake :-)

[Qqwy]

I've added a call that turns a normal Porter request into a Porter.Multi request, for compatibility's sake :-)

[peterszerzo]

In order to make sure newcomers to the library don't jump straight to this module and get frustrated, I think it makes sense to start this documentation saying something like This is an advanced version of the Porter module that covers ... For most use-cases, using Porter should be sufficient. If, however, you have a tangible issue with expressing chaining and transformations with your port messages, read along :).

I feel like your use-case is on the advanced side, and it would be nice to make sure people don't jump in straight away unless it gives them a real benefit.

[Qqwy]

This change has been made. I hope the wording I ended up using meets your expectations :-).