update docs for HandlerExcepton and GRPC.Logger

lib/grpc/logger.ex

@@ -0,0 +1,9 @@
+defmodule GRPC.Logger do
+  @doc """
+  Normalizes the exception and stacktrace inputs by its kind to match the format specified for `crash_report` metadata
+  in [Logger](https://hexdocs.pm/logger/main/Logger.html#module-metadata)
+  """
+  def crash_reason(:throw, reason, stacktrace), do: {{:nocatch, reason}, stacktrace}
+  def crash_reason(:error, reason, stack), do: {Exception.normalize(:error, reason, stack), stack}
+  def crash_reason(:exit, reason, stacktrace), do: {reason, stacktrace}
+end

lib/grpc/server/adapters/cowboy/handler_exception.ex

@@ -1,4 +1,8 @@
 defmodule GRPC.Server.Adapters.Cowboy.HandlerException do
+  @moduledoc """
+  Exception meant to represent failures captured in Cowboy.Handler
+  """
+
   defexception [:req, :kind, :reason, :stack]
 
   def new(req, %{__exception__: _} = exception, stack \\ [], kind \\ :error) do