I've a manged package which uses an external API to load some data, and each installation of this package in different orgs require an specific API Key to authenticate against the API.
This APIKey is stored in a hierarchical custom setting, and the setting object is shipped with the package (except the value which is fine).
What I would like to do is prompt user for their APIKey at the installation time (using an InstallHandler as Post Install Handler/VisualForce combination), and add the value to the configuration object.
But I'm unable to find a reference on how to use a VisualForce page from an InstallHandler. Is it possible, or is InstallHandler an entirely background process?
If this method is not practical, what is the recommended way to collect user choices at the package installation time?