Constant input might be a good idea

[Oberacda]

Feature Request

Description

In some cases, a constant input is required. Of course, we can use an extra node, but setting some input to a constant might be useful.
Example: The service node with an empty service.
Allowing users to set inputs to constants might reduce boilerplate nodes and node duplication (Service vs ServiceOption).
It might be useful to allow an input to be set via static value or external data connection.
However, I would prefer a switch for each input on the node to determine which input source should be used.