Refactor generated to returning keyword in order to return the correct type

[gustavoamigo]

Fixes #427

Problem

Right now, the generated parameter in schema is limited to Long. If the primary key is not a type that can be casted safely to Long, like UUID, it limits its use.

Solution

Create new keyword returning which will allow other types to be returned. Example:

case class Entity(name: String, id: Option[UUID] = None)
val q = quote {
        query[Entity].insert.returning(_.id)
      }
val id: Option[UUID] = db.run(q)(Entity("test"))

Notes

Additional notes.

Checklist

• Unit test all changes
• Update README.md if applicable
• Add [WIP] to the pull request title if it's work in progress
• Squash commits that aren't meaningful changes
• Run sbt scalariformFormat test:scalariformFormat to make sure that the source files are formatted

@getquill/maintainers

[mdedetrich]

@gustavoamigo Looking good from here!

[fwbrasil]

Can we avoid the implicit class here?

[gustavoamigo]

I'll try

[gustavoamigo]

no lucky trying to remove the implicit class. I tried to create a trait that extends T => UnassignedAction[T] with Insert[T], but it breaks macros. It seems to be easier to just use implicit class.

[gustavoamigo]

@getquill/maintainers the ActionApply will not work inherited from Function1 and both type parameters open. I will have to refactor it to use a generic ActionApply that does not inherit Function1. In this branch ActionApply is disable for the quill-jdbc and quill-async module. Are you guys ok if I fix this issue in another PR, so I can finish this one earlier?

BTW, there are a few things I need to do like docs and tests, but this branch is ready for testing.

[gustavoamigo]

@getquill/maintainers This PR is ready for review (if it builds). As I said, I removed ActionApply from quill-jdbc and quill-async, since it is buggy to inherit from Fuction1. I would like to refactor ActionApply in another PR.

[fwbrasil]

I think we could remove this example or replace it by another one now that returning id is supported by the DSL.

[gustavoamigo]

@getquill/maintainers all right, I think this PR is ready for merging.