Choose a destination after signup

In the active site or module, include zotonic.hrl and export observe_signup_confirm_redirect/2:

observe_signup_confirm_redirect(#signup_confirm_redirect{}, Context) ->
    m_rsc:p(signup_welcome, page_url, Context).

Create a resource named signup_welcome, publish it and verify the new user can view it. Compile, refresh observer registration, then complete a practice signup and its verification flow. Expect the welcome page.

This notification is for a signup with a confirmed identity. For normal login, the separate #logon_ready_page{request_page = RequestedPage} notification participates in destination selection. Preserve a legitimate existing destination when the flow requires it and validate any supplied URL using the authentication module's policy. Do not return an arbitrary posted URL or obsolete raw tuple.