Slack notifier implementation (#1)

* Initial commit

* Replace receive do with assert_receive in test

* Move lib modules to lib/boom_slack_notifier

* Make behaviour return types generic to allow user-defined http adapters

* Add error logging when request fails and testing for it

* Readme improvements

* Move test process registration to helper module

* Improve logger formatting to allow error objects

* Rename HttpAdapter into SlackAdapter, removed nesting and updated docs

* Move out HTTPoisonAdapter to lib folder

* Remove unnecessary Application.put_env in tests

* Fix format

* Rename slack adapater references in documentation

* Rename cache key

.formatter.exs

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+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

.github/workflows/elixir.yml

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+name: Elixir CI
+
+on: [push, pull_request]
+
+jobs:
+  build:
+
+    name: Build and test
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - elixir: '1.8'
+            otp: '21'
+          - elixir: '1.8'
+            otp: '22'
+          - elixir: '1.9'
+            otp: '21'
+          - elixir: '1.9'
+            otp: '22'
+          - elixir: '1.10'
+            otp: '21'
+          - elixir: '1.10'
+            otp: '22'
+          - elixir: '1.10'
+            otp: '23'
+          - elixir: '1.11'
+            otp: '21'
+          - elixir: '1.11'
+            otp: '22'
+          - elixir: '1.11'
+            otp: '23'
+          - elixir: '1.11'
+            otp: '24'
+          - elixir: '1.12'
+            otp: '22'
+          - elixir: '1.12'
+            otp: '23'
+          - elixir: '1.12'
+            otp: '24'
+          - elixir: '1.12'
+            otp: '24'
+          - elixir: '1.13'
+            otp: '22'
+          - elixir: '1.13'
+            otp: '23'
+          - elixir: '1.13'
+            otp: '24'
+            lint: lint
+          - elixir: '1.13'
+            otp: '24'
+            deps: latest
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Set up Elixir
+      uses: erlef/setup-beam@v1
+      with:
+        elixir-version: ${{ matrix.elixir }}
+        otp-version: ${{ matrix.otp }}
+
+    - name: Retrieve Mix Dependencies Cache
+      if: matrix.deps != 'latest'
+      uses: actions/cache@v1
+      id: mix-cache
+      with:
+        path: deps
+        key: ${{ runner.os }}-${{ matrix.otp }}-${{ matrix.elixir }}-mix-${{ hashFiles('mix.lock') }}
+
+    - name: Remove mix.lock
+      if: matrix.deps == 'latest'
+      run: rm mix.lock
+
+    - name: Install dependencies
+      if: steps.mix-cache.outputs.cache-hit != 'true'
+      run: mix deps.get
+
+    - name: Retrieve PLT Cache
+      uses: actions/cache@v1
+      id: plt-cache
+      with:
+        path: priv/plts
+        key: ${{ runner.os }}-${{ matrix.otp }}-${{ matrix.elixir }}-plts-${{ hashFiles('mix.lock') }}
+      if: ${{ matrix.lint }}
+
+    - name: Create PLTs
+      run: |
+        mkdir -p priv/plts
+        mix dialyzer --plt
+      if: ${{ matrix.lint }}
+
+    - name: Check quality
+      run: |
+        mix format --check-formatted
+        mix dialyzer --no-check
+      if: ${{ matrix.lint }}
+
+    - name: Run tests
+      run: mix test

.gitignore

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+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Ignore .fetch files in case you like to edit your project deps locally.
+/.fetch
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+boom_slack_notifier-*.tar
+
+# Temporary files, for example, from tests.
+/tmp/
+
+priv/

README.md

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+# BoomSlackNotifier
+
+Provides a Slack notifier for the [BoomNotifier](https://github.com/wyeworks/boom) exception notification package.
+
+You can read the full documentation at [https://hexdocs.pm/boom_slack_notifier](https://hexdocs.pm/boom_slack_notifier).
+
+## Installation
+
+The package can be installed by adding `boom_slack_notifier` to your list of dependencies in
+`mix.exs`:
+
+```elixir
+def deps do
+  [
+    {:boom_notifier, "~> 0.8.0"},
+    {:boom_slack_notifier, "~> 0.1.0"}
+  ]
+end
+```
+
+## How to use it
+
+```elixir
+defmodule YourApp.Router do
+  use Phoenix.Router
+
+  use BoomNotifier,
+    notifier: BoomSlackNotifier.SlackNotifier,
+    options: [
+      webhook_url: "<your-slack-generated-url>",
+    ]
+
+  # ...
+```
+
+To configure it, you need to set the `webhook_url` in the `options` keyword list. A `POST` request with a `json` will be made to that webhook when an error ocurrs with the relevant information.
+
+### Setting up a Slack webhook
+
+If you don't already have a webhook setup for Slack, you can follow the steps below:
+
+1. Go to [Slack API](https://api.slack.com/) > My Apps
+2. Create a new application
+3. Inside your new application go to > Add features and functionality > Incoming Webhooks
+4. Activate incoming webhooks for your application
+5. Scroll down to 'Webhook URLs for Your Workspace' and create a new Webhook URL for a given channel.
+
+## Http client
+
+By default BoomSlackNotifier uses [HTTPoison](https://github.com/edgurgel/httpoison) as the http client. 
+
+You can setup your favorite client by warpping it with the `SlackAdapter` behaviour, for example:
+
+```
+#mojito_http_adapter.ex
+
+  @impl BoomSlackNotifier.SlackAdapter
+  @spec post(any, binary, any) :: {:ok, any} | {:error, any}
+  def post(body, url, headers) do
+    {:ok, response} = Mojito.request(body: body, method: :post, url: url, headers: headers)
+    # ...
+  end
+```
+
+And then specifying it in your application configuration:
+
+```
+#config.exs
+
+config :boom_slack_notifier, :slack_adapter, MyApp.MojitoHttpAdapter
+
+```
+
+Default configuration (not required): 
+```
+config :boom_slack_notifier, :slack_adapter, BoomSlackNotifier.SlackClient.HTTPoisonAdapter
+```
+## License
+
+BoomSlackNotifier is released under the terms of the [MIT License](https://github.com/wyeworks/boom/blob/master/LICENSE).

config/config.exs

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+use Mix.Config
+
+config :phoenix, :json_library, Jason
+
+import_config "#{Mix.env()}.exs"

config/dev.exs

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+use Mix.Config
+
+config :boom_slack_notifier, :slack_adapter, BoomSlackNotifier.HTTPoisonAdapter

config/test.exs

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+use Mix.Config
+
+config :boom_slack_notifier, :slack_adapter, Support.HttpAdapterMock

lib/boom_slack_notifier/httpoison_adapter.ex

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+defmodule BoomSlackNotifier.HTTPoisonAdapter do
+  @moduledoc false
+
+  @behaviour BoomSlackNotifier.SlackAdapter
+
+  HTTPoison.start()
+
+  @impl BoomSlackNotifier.SlackAdapter
+  @spec post(any, binary, HTTPoison.Base.headers()) ::
+          {:ok,
+           HTTPoison.Response.t() | HTTPoison.AsyncResponse.t() | HTTPoison.MaybeRedirect.t()}
+          | {:error, HTTPoison.Error.t()}
+  def post(body, url, headers) do
+    HTTPoison.post(url, body, headers, [])
+  end
+end

lib/boom_slack_notifier/slack_adapter.ex

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+defmodule BoomSlackNotifier.SlackAdapter do
+  @moduledoc """
+
+  By default BoomSlackNotifier uses [HTTPoison](https://github.com/edgurgel/httpoison) as the http client.
+
+  You can setup your favorite client by warpping it with the `SlackAdapter` behaviour, for example:
+
+  ```
+  #mojito_http_adapter.ex
+
+  @impl BoomSlackNotifier.SlackAdapter
+  @spec post(any, binary, any) :: {:ok, any} | {:error, any}
+  def post(body, url, headers) do
+    {:ok, response} = Mojito.request(body: body, method: :post, url: url, headers: headers)
+    # ...
+  end
+  ```
+
+  And then specifying it in your application configuration:
+
+  ```
+  #config.exs
+
+  config :boom_slack_notifier, :slack_adapter, MyApp.MojitoHttpAdapter
+
+  ```
+
+  Default configuration (not required):
+  ```
+  config :boom_slack_notifier, :slack_adapter, BoomSlackNotifier.SlackClient.HTTPoisonAdapter
+  ```
+  """
+
+  @doc """
+  Defines a callback to be used by the http adapters
+  """
+  @callback post(any, binary, any) :: {:ok, any} | {:error, any}
+end