Remove CI image

[jlledom]

This closes several issues under https://github.com/3scale/apisonator/issues/352

• https://github.com/3scale/apisonator/issues/354
  • Adds a podman-compose.yml file to quickly launch the Redis services locally (https://github.com/3scale/apisonator/pull/370/commits/acb047b1717bb07094a52471f6893eae6b7999af)
• https://github.com/3scale/apisonator/issues/355
  • Allows having different .env files for development and test (https://github.com/3scale/apisonator/pull/370/commits/7ec4d823c6f7e53005a360396a53d54ada6015fc)
  • Updates tests so they can run out of the CI container (https://github.com/3scale/apisonator/pull/370/commits/83b518108c033b127f6ac0ae7afe3b8d982ef680)
  • Updates the CircleCI workflow to not require a CI image anymore (https://github.com/3scale/apisonator/pull/370/commits/9ab0f9856df44e890560d069ce9177120fe656e6)
  • Implement a few fixes that were making the tests fail (https://github.com/3scale/apisonator/pull/370/commits/addbbcc6f5ec7ea02ce0451637dfbd405690b2ae), (https://github.com/3scale/apisonator/pull/370/commits/be00cd9f314237e58661bf0950372ac8bceee91e) and (https://github.com/3scale/apisonator/pull/370/commits/d1fa8fc7537946c5564d7986f0e67ff339afb808).
  • I suspect tests were actually always running in sync mode.
• https://github.com/3scale/apisonator/issues/357
  • Update documentation (https://github.com/3scale/apisonator/pull/370/commits/8588fb6277cb1b4574f89d6b6ddc1bbf95d338a4)
• https://github.com/3scale/apisonator/issues/356
  • Clean up unused scripts and configs (https://github.com/3scale/apisonator/pull/370/commits/3c4291d64f0c28049639a060cab6ee5d37b68198) and simplify the two scripts we still would want to use (https://github.com/3scale/apisonator/pull/370/commits/480b76113aa3b5ab8be83bfd036c5fe5f2ba186b)

[mayorova]

That's a huuuuge improvement! Thanks @jlledom ! I've left some comments.

[jlledom]

@akostadinov @mayorova I think I addressed all your comments.