Initial extraction from InfluxData

[randycoulman]

Closes #1

This contains the code almost exactly as it has been running in production at InfluxData. We're open to make any changes or improvements necessary to get this in good shape for a wider community.

• Generated initial app skeleton:

  • mix new . --app config_cat
  • Don't overwrite README or .gitignore.
  • Append the README contents that would have been generated to the existing README. They're not accurate until we publish to hex.pm, but I didn't want to lose the content.

• Extract library from InfluxData's app. I made the following changes to what we have running:

  • Add necessary dependencies to mix.exs.
  • Replace use of Ecto.UUID.generate/0 with UUID.uuid4/0 to avoid depending on Ecto.
  • Configure the log level in test_helper.exs (we had it in application config, but that's not recommended for libraries).
  • Add @tag capture_log: true to noisy tests. See note below.

NOTES:

• I'm using Elixir 1.10.4; I tried using 1.11, but we get a warning from the elixir_uuid library regarding its use of the :crypto library. Elixir 1.11 does some extra checking of this sort. This is an open PR to address this: Adds :crypto as a dependency in extra_applications zyro/elixir-uuid#47. We'll ultimately need to decide which Elixir versions we want to support and configure those in the Travis build matrix.

• I added mix_test_watch as a dev-only dependency. It's very handy to be able to run mix test.watch --stale while developing so that tests run automatically as you make changes.

• I attempted to add some tests around the log output, but because the logging comes from a separate process, it's harder to capture that way. If this is something we want tests around, we can do that as separate PR.

[igorescobar]

FYI: I've created a branch called v1.0.0 based on the main branch. Let's target all upcoming PRs to this one instead of the main branch. After we feel it's time we can merge the v1.0.0 branch to the main one. 👍

[igorescobar]

@randycoulman The fact you are working on a fork means I can't push to the same PR as you and we can't collaborate on the same PR.

So I pushed your changes (along with some of mine) to this branch instead:
https://github.com/configcat/elixir-sdk/tree/pr/randycoulman/2

[igorescobar]

Or, if you prefer, you can try to address the changes @laliconfigcat suggested and I can jump in later.

[randycoulman]

@laliconfigcat I've gone through all of your comments and extracted them to new issues. Now that we're on a 1.0 branch, can we go ahead and merge this as-is and then start addressing the issues in separate PRs? This is already a pretty big PR and I think it'll be easier to review the various changes separately. Thanks!