Add a server layer to a tower. This layer
will run before the 'shiny' app's server function. This
is useful for adding custom logic to the server function
without modifying the original server function.
Usage
add_server_layer(tower, layer)
Arguments
- tower
A tower
- layer
A function that takes input, output, and session
and has no return value. This function will be called before
the original server function. If you want to short-circuit
the server use an exception.
Value
The tower with the added layer