context helpers, rework logging to support ongoing inheritance

Leaves module logger property as purely an override, pulling logger
information directly from the lifecycle instead.

module.go

@@ -13,15 +13,23 @@ var ErrModuleNotFound = errors.New("module not found")
 // moduleFn is a function type for module setup and teardown functions.
 type moduleFn func(*Module) error
 
+// GenericModule is an interface that allows modules to be extended with custom
+// functionality, as the module can return a pointer to the underlying Module.
+type GenericModule interface {
+	// Module returns the underlying Module instance.
+	Module() *Module
+}
+
 // Module represents a sub-system of the application, with its setup and
 // teardown functions and dependencies.
 type Module struct {
-	logger   *slog.Logger
-	name     string
-	setup    moduleFn
-	teardown moduleFn
-	depends  []string
-	loaded   bool // loaded indicates if the module has been set up
+	lifecycle *Lifecycle // lifecycle is the parent lifecycle this module belongs to
+	logger    *slog.Logger
+	name      string
+	setup     moduleFn
+	teardown  moduleFn
+	depends   []string
+	loaded    bool // loaded indicates if the module has been set up
 }
 
 // ModuleOpts contains user-exposed options when defining a module.
@@ -45,12 +53,13 @@ func NewModule(name string, opts ModuleOpts) *Module {
 	}
 }
 
-// Logger returns the logger for the module.
+// Logger returns the logger for the module. Uses the lifecycle's logger unless
+// a specific logger has been set during module load.
 func (s *Module) Logger() *slog.Logger {
-	if s.logger == nil {
-		panic(fmt.Sprintf("module %s used before logger was initialized", s.name))
+	if s.logger != nil {
+		return s.logger
 	}
-	return s.logger
+	return s.lifecycle.Logger()
 }
 
 // Name returns the name of the module.
@@ -58,6 +67,11 @@ func (s *Module) Name() string {
 	return s.name
 }
 
+// String returns the name of the module in square brackets, e.g. "[module-name]".
+func (s *Module) String() string {
+	return fmt.Sprintf("[%s]", s.name)
+}
+
 // Loaded returns whether the module has been set up.
 func (s *Module) Loaded() bool {
 	return s.loaded