Flake: support integers in from_string/1

Some previously issued stateless tokens have integer ids in them.

lib/pleroma/flake_id.ex

@@ -33,6 +33,10 @@ def to_string(flake = <<_::integer-size(64), _::integer-size(48), _::integer-siz
 
   def to_string(s), do: s
 
+  def from_string(int) when is_integer(int) do
+    from_string(Kernel.to_string(int))
+  end
+
   for i <- [-1, 0] do
     def from_string(unquote(i)), do: <<0::integer-size(128)>>
     def from_string(unquote(Kernel.to_string(i))), do: <<0::integer-size(128)>>

test/flake_id_test.exs

@@ -11,6 +11,7 @@ defmodule Pleroma.FlakeIdTest do
     test "from_string/1" do
       fake_flake = <<0::integer-size(64), 42::integer-size(64)>>
       assert from_string("42") == fake_flake
+      assert from_string(42) == fake_flake
     end
 
     test "zero or -1 is a null flake" do