[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/utils/cli_utils.ex

@@ -13,17 +13,22 @@ defmodule Pinchflat.Utils.CliUtils do
   commands if the job runner is cancelled.
 
   Delegates to `System.cmd/3` and any options/output
-  are passed through.
+  are passed through. Custom options can be passed in.
+
+  Custom options:
+    - logging_arg_override: if set, the passed value will be logged in place of
+      the actual arguments passed to the command
 
   Returns {binary(), integer()}
   """
-  def wrap_cmd(command, args, opts \\ []) do
+  def wrap_cmd(command, args, passthrough_opts \\ [], opts \\ []) do
     wrapper_command = Path.join(:code.priv_dir(:pinchflat), "cmd_wrapper.sh")
     actual_command = [command] ++ args
+    logging_arg_override = Keyword.get(opts, :logging_arg_override, Enum.join(args, " "))
 
-    Logger.info("[command_wrapper]: #{command} called with: #{Enum.join(args, " ")}")
+    Logger.info("[command_wrapper]: #{command} called with: #{logging_arg_override}")
 
-    System.cmd(wrapper_command, actual_command, opts)
+    System.cmd(wrapper_command, actual_command, passthrough_opts)
   end
 
   @doc """

lib/pinchflat/utils/filesystem_utils.ex

@@ -5,6 +5,21 @@ defmodule Pinchflat.Utils.FilesystemUtils do
   alias Pinchflat.Media
   alias Pinchflat.Utils.StringUtils
 
+  @doc """
+  Checks if a file exists and has non-whitespace contents.
+
+  Returns boolean()
+  """
+  def exists_and_nonempty?(filepath) do
+    case File.read(filepath) do
+      {:ok, contents} ->
+        String.trim(contents) != ""
+
+      _ ->
+        false
+    end
+  end
+
   @doc """
   Generates a temporary file and returns its path. The file is empty and has the given type.
   Generates all the directories in the path if they don't exist.