Replace Poison with Jason

[unnawut]

Subject of the issue

While @ripzery was toying with map-json conversion. He found out that some subapps were using poison while other subapps have already moved on to Jason.

Last time checked it was due to some libraries' hard dependency on Poison. Maybe it's time to revisit again now that we are on Elixir 1.8 and Ecto 3.

Your environment

N/A

Steps to reproduce

N/A.

Expected behavior

N/A

Actual behavior

N/A

[Macavirus]

Here's a list of the libraries currently using Poison... Some of these have blockers that are fixed in unmerged PRs that we could set a calendar data to review, others are resolved by moving to newer versions or alternative libraries.

• appsignal - Plans to migrate to Jason (progress in this issue here ) https://github.com/appsignal/appsignal-elixir/issues/474
• arc - No relevant issue yet https://github.com/stavro/arc
• bamboo - Has unmerged PR https://github.com/thoughtbot/bamboo/pull/485 but also potentially already supports configuration to depend on Jason instead: https://github.com/thoughtbot/bamboo/issues/440
• chaperon - No relevant issue yet https://github.com/polleverywhere/chaperon
• cloak - Already supports Jason https://github.com/danielberkompas/cloak/issues/44
• ecto - Already supports Jason
• ex_aws - Supports Jason in config https://github.com/ex-aws/ex_aws/issues/616
• goth - Supports Jason in newer version https://github.com/peburrows/goth/pull/48
• instream - No relevant issue yet https://github.com/mneudert/instream
• jason_web_token No relevant issue yet https://github.com/garyf/json_web_token_ex May be worth switching to better-supported Joken
• phoenix Already supports Jason in newer version >1.4 https://github.com/phoenixframework/phoenix/pull/2734

[unnawut]

We don't even have to wait for the dependencies to update. We still use Poison in some places in the ewallet. Those should be replaceable immediately and be gone with :poison as our direct dependencies. @Macavirus let us know if you'd like to tackle that. ❤️