This is a basic hook that loads the current tenant assign from a given value set on subdomain.

Options:

• :assign (atom/0) - The key to use when assigning the current tenant The default value is :current_tenant.

• :handle_subdomain - An mfa to call with the socket and a subdomain value. Can be used to do something like fetch the current user given the tenant.

      Must return either `{:cont, socket}`, `{:cont, socket, opts} or `{:halt, socket}`.

  To use the hook, you can do one of the following:

  live_session :foo, on_mount: [
  AshPhoenix.LiveView.SubdomainHook,
  ]

  This will assign the tenant's subdomain value to :current_tenant key by default.

  If you want to specify the assign key

  live_session :foo, on_mount: [
  {AshPhoenix.LiveView.SubdomainHook, [assign: :different_assign_key}]
  ]

  You can also provide handle_subdomain module, function, arguments tuple that will be run after the tenant is assigned.

  live_session :foo, on_mount: [
  {AshPhoenix.LiveView.SubdomainHook, [handle_subdomain: {FooApp.SubdomainHandler, :handle_subdomain, [:bar]}]
  ]

  This can be any module, function, and list of arguments as it uses Elixir's apply/3.

  The socket and tenant will be the first two arguments.

  The function return must match Phoenix LiveView's on_mount/1

  defmodule FooApp.SubdomainHandler do
  def handle_subdomain(socket, tenant, :bar) do
    # your logic here
    {:cont, socket}
  end
  end