The last option in the list of providers should be named "Custom", and use @drawable/ic_provider_generic.
On click it should open a dialog for the query, and bypass the normal persistence flow
The dialog should show the duckduckgo unformatted url as the hint, unless a custom url was already set.
Dialog title: "Add custom provider". Positive button: "Select"
The dialog, on click of the positive button, should verify the url contains exactly one token/placeholder, and is a valid url (the Android validator should suffice).
** If not verified, display toast "Incorrectly formatted address.". The dialog should not be closed.
If verified, persist choice.
@drawable/ic_provider_generic.