figure out what to about the shapeless code in the parsing module

[pjfanning]

• relates to #35
• Unlike #1, there is no decision to remove the shapeless code yet.
• it could be that if #1 is merged, that we no longer need the shapeless code (I haven't checked if the parboiled2 code is the only code using the shapeless code)
• shapeless3 exists for Scala 3 but does include HList - I guess the logic is that Scala 3 tuples can do the task
• so if we do use HLIst or the other shapeless code in pekko-http (after #1 is merged or deferred) then we might want to keep the shapeless code
• if we keep it, we will need to consider updating our LICENSE and NOTICE.
  • https://github.com/milessabin/shapeless has no NOTICE
  • it is Apache licensed so we may need to document it in our license (this needs to be verified)
• relates to #62

[mdedetrich]

Regarding Scala 3, Scala has apparently added HLists and other datastructures which shapeless has historically been used for (see https://www.scala-lang.org/2021/02/26/tuples-bring-generic-programming-to-scala-3.html), so one thing we can look into is to remove shapeless for Scala 3 specifically

[pjfanning]

this code was removed alongside the parboiled code