Allow passing custom methods

[sebastian-palma]

Allows passing custom method name that can be interpolated for creating the dump, e.g find_or_create_by:

Movie.all
# [#<Movie:0x00007f89f799f9e8 id: 1, name: "Machuca", status: nil, created_at: Sat, 06 Jun 2020 20:45:27 UTC +00:00, updated_at: Sat, 06 Jun 2020 20:45:27 UTC +00:00>,
   #<Movie:0x00007f89f799f920 id: 2, name: "Burned after reading", status: nil, created_at: Sat, 06 Jun 2020 20:45:39 UTC +00:00, updated_at: Sat, 06 Jun 2020 20:45:39 UTC +00:00>]

SeedDump.dump(Movie, method: :find_or_create_by)
   (0.4ms)  SELECT COUNT(*) FROM "movies"
   (0.3ms)  SELECT COUNT(*) FROM "movies"
  Movie Load (0.3ms)  SELECT "movies".* FROM "movies" LIMIT $1 OFFSET $2  [["LIMIT", 2], ["OFFSET", 0]]
# "Movie.find_or_create_by([\n  {name: \"Machuca\", status: nil},\n  {name: \"Burned after reading\", status: nil}\n])\n"

or find_or_create_by! or create_or_find_by or whatever you want.