Add terms acceptance

[joshsmith]

Problem

On the payments settings page we need to add a Stripe terms acceptance. I believe we should add this at the "create account" step.

We'll need to collect the IP address, browser user agent, and the time the form was submitted as a Unix timestamp.

The text will display a link to our terms of service and to Stripe's terms of service.

By registering your account, you agree to our Terms of Use and the Stripe Connected Account Agreement.

[joshsmith]

conn.remote_ip |> Tuple.to_list |> Enum.join(".")

conn.req_params["user-agent"]
https://stripe.com/docs/api/curl#account_object-tos_acceptance

We can just send up legal_entity_tos_acceptance_date and then set legal_entity_tos_acceptance_ip and _user_agent with the conn values.