[Enhancement] Custom media lifecycle scripts (#219)

* Namespaced notification modules under lifecycle

* Added a JSON encoder for all the main model types

* Added startup task to create user script file

* Hook up user script event to media download

* Hooked up media deletion user script

* Added jq to docker deps

* Updated README

lib/pinchflat/lifecycle/notifications/command_runner.ex

@@ -0,0 +1,64 @@
+defmodule Pinchflat.Lifecycle.Notifications.CommandRunner do
+  @moduledoc """
+  Runs apprise commands using the `System.cmd/3` function
+  """
+
+  require Logger
+
+  alias Pinchflat.Utils.CliUtils
+  alias Pinchflat.Utils.FunctionUtils
+  alias Pinchflat.Lifecycle.Notifications.AppriseCommandRunner
+
+  @behaviour AppriseCommandRunner
+
+  @doc """
+  Runs an apprise command and returns the string output.
+  Can take a single server string or a list of servers as well as additional
+  arguments to pass to the command.
+
+  Returns {:ok, binary()} | {:error, :no_servers} | {:error, binary()}
+  """
+  @impl AppriseCommandRunner
+  def run(nil, _), do: {:error, :no_servers}
+  def run("", _), do: {:error, :no_servers}
+  def run([], _), do: {:error, :no_servers}
+
+  def run(endpoints, command_opts) do
+    endpoints = List.wrap(endpoints)
+    default_opts = [:verbose]
+    parsed_opts = CliUtils.parse_options(default_opts ++ command_opts)
+
+    {output, exit_code} = CliUtils.wrap_cmd(backend_executable(), parsed_opts ++ endpoints)
+    Logger.info("[apprise] response: #{output}")
+
+    case exit_code do
+      0 -> {:ok, String.trim(output)}
+      _ -> {:error, String.trim(output)}
+    end
+  end
+
+  @doc """
+  Returns the version of apprise as a string.
+
+  Returns {:ok, binary()} | {:error, binary()}
+  """
+  @impl AppriseCommandRunner
+  def version do
+    case CliUtils.wrap_cmd(backend_executable(), ["--version"]) do
+      {output, 0} ->
+        output
+        |> String.split(~r{\r?\n})
+        |> List.first()
+        |> String.replace("Apprise", "")
+        |> String.trim()
+        |> FunctionUtils.wrap_ok()
+
+      {output, _} ->
+        {:error, output}
+    end
+  end
+
+  defp backend_executable do
+    Application.get_env(:pinchflat, :apprise_executable)
+  end
+end