Loads the host's validated Attesto configuration into conn.private.

AttestoPhoenix controllers use two immutable configuration values:

• %AttestoPhoenix.Config{} under :attesto_phoenix_config
• the derived %Attesto.Config{} under :attesto_protocol_config

Mount this plug in the pipeline passed to AttestoPhoenix.Router.attesto_routes/1:

pipeline :attesto_phoenix_config do
  plug AttestoPhoenix.Plug.PutConfig, otp_app: :my_app
end

scope "/" do
  attesto_routes(pipeline: :attesto_phoenix_config)
end

The explicit :otp_app option is preferred. When it is omitted, the plug reads config :attesto_phoenix, otp_app: :my_app at request time. Existing correctly typed private values are preserved, which lets a host install a request-specific configuration earlier in the pipeline. A preinstalled protocol config must exactly match the value derived from that request's host config; otherwise the plug fails closed instead of advertising policy that the token endpoints do not enforce. A value of the wrong type also fails closed instead of being silently replaced. This plug is the reference implementation and convenient route helper for installing both private values, but hosts may also populate them directly using custom plugs. Library controllers and AttestoPhoenix.Plug.Authenticate bind the private configuration only while their bounded work executes; this plug does not retain tenant state in the process dictionary between pipeline and action dispatch.