Handling lists in extract step body conversions

[RyanRConaway]

Ticket Link #1049

Description

Passing a list into the body of an http extract step causes Andi to error out. This PR allows for the body of an extract http step to be a list as well.

Reminders:

• Be mindful of impacts of changing Major/Minor/Patch versions of each elixir app:
  • If updating patch version, are you sure there are no chart changes required to maintain functionality? If so, you should bump minor version instead.
  • If updating Major or Minor versions , did you update the sauron chart configuration?
• If changing elixir code in an "app", did you update the relevant version
  in mix.exs?
• If altering an API endpoint, was the relevant postman collection updated?
  • If a new version of smart_city is being used (new fields on a struct), were the relevant postman collections updated?