refactor: aggiunta documentazione sull'architettura e varie migliorie qua e là

sl/sl.go

@@ -1,6 +1,12 @@
 // The [sl] package has two main concepts, the [ServiceLocator] itself is the main object that one should pass around through the application. A [ServiceLocator] has a list of slots that can be filled with [InjectLazy] and [InjectValue] and retrieved with [Use]. As slots should be unique they can only be created with the [NewSlot] function.
 //
 // The usual way to use this module is to make slots for go interfaces and then pass implementations using the [InjectValue] and [InjectLazy] functions.
+//
+// Services can be of various types:
+// - a service with no dependencies can be directly injected inside a ServiceLocator using [InjectValue].
+// - a service with dependencies on other service should use [InjectLazy]. This lets the service to initialize itself when required and makes the developer not think the topological sort to put onto the DAG of service dependencies.
+// - a service can also be private, in this case the slot for a service should be a private field in the service package. This kind of services should also provide a way to inject them into a ServiceLocator.
+// - a package also just provide a slot. This is useful for using the ServiceLocator to easily pass around values, effectively threating slots just as dynamically scoped variables.
 package sl
 
 import (
@@ -12,7 +18,7 @@ import (
 // Logger is the debug logger, in the future this will be disabled and discard by default.
 //
 // As this is the service locator module it was meaning less to pass this through the ServiceLocator itself (without making the whole module more complex)
-var Logger *log.Logger = log.New(os.Stderr, "[sl]", log.LstdFlags)
+var Logger *log.Logger = log.New(os.Stderr, "[sl] ", log.Lmsgprefix)
 
 // slot is just a "typed" unique "symbol".
 type slot[T any] *struct{}