Generic JSON encoder for case-classes

[otto-dev]

Allows conversion of any Scala case class and tuples to/from JSON by importing mist.api.encoding.defaults._. Makes it unnecessary to create encoders for case classes.

Encoders for specific classes (case classes) will continue to take precedence over this generic encoder and extractor. Hence the ability to create specific encoders remains unaffected, and existing code will not break.

Derived from the examples in the documentation. I can't build and test mist locally beyond compilation because of time constrains.

I'm not sure if the import of shadedshapeless.Lazy is necessary.

Also, feel free to reject this pull request if there is a reason why this hasn't been implemented yet.

[otto-dev]

CI fails with a python syntax error thrown by a third party module pytest

[dos65]

I think it would be better to choose the most standard way in the ecosystem and put these instances into auto object. Like circe and pureconfig do this.

[otto-dev]

Sounds good to me. As long as you have a way to delegate the encoder creation to Scala. Planning to have a look when I find time, unless someone beats me to it. I first have to set up the build & test environment.