Set the rich media cache based on the expiration time of image.

Adopt behaviour Pleroma.Web.RichMedia.Parser.TTL

Example

defmodule MyModule do
  @behaviour Pleroma.Web.RichMedia.Parser.TTL
  def ttl(data, url) do
    image_url = Map.get(data, :image)
    # do some parsing in the url and get the ttl of the image
    # and return ttl is unix time
    parse_ttl_from_url(image_url)
  end
end

Define the module in the config

config :pleroma, :rich_media,
  ttl_setters: [MyModule]