Remove checks and return all errors in config validation

internal/config/config.go

@@ -1,6 +1,7 @@
 package config
 
 import (
+	"errors"
 	"fmt"
 	"os"
 	"strings"
@@ -47,25 +48,11 @@ type Configuration struct {
 
 func (c Configuration) Validate() error {
 	// TODO: should this validate all the fields in Configuration?
-	if config, ok := interface{}(c.Upload).(ConfigurationValidator); ok {
-		err := config.Validate()
-		if err != nil {
-			return err
-		}
-	}
-	if config, ok := interface{}(c.API.Auth).(ConfigurationValidator); ok {
-		err := config.Validate()
-		if err != nil {
-			return err
-		}
-	}
-	if config, ok := interface{}(c.Preprocessing).(ConfigurationValidator); ok {
-		err := config.Validate()
-		if err != nil {
-			return err
-		}
-	}
-	return nil
+	apiAuthErr := c.API.Auth.Validate()
+	preprocessingErr := c.Preprocessing.Validate()
+	uploadErr := c.Upload.Validate()
+
+	return errors.Join(apiAuthErr, preprocessingErr, uploadErr)
 }
 
 func Read(config *Configuration, configFile string) (found bool, configFileUsed string, err error) {