Improve encryption internals and fix a few bugs therein (#2551)

Signed-off-by: Christian Mesh <christianmesh1@gmail.com>
Signed-off-by: yottta <andrei.ciobanu@opentofu.org>
Co-authored-by: yottta <andrei.ciobanu@opentofu.org>
Co-authored-by: Martin Atkins <mart@degeneration.co.uk>

internal/encryption/method/unencrypted/method.go

@@ -6,6 +6,7 @@
 package unencrypted
 
 import (
+	"github.com/opentofu/opentofu/internal/encryption/config"
 	"github.com/opentofu/opentofu/internal/encryption/method"
 )
 
@@ -19,12 +20,12 @@ func (f *descriptor) ID() method.ID {
 	return "unencrypted"
 }
 func (f *descriptor) ConfigStruct() method.Config {
-	return new(config)
+	return new(methodConfig)
 }
 
-type config struct{}
+type methodConfig struct{}
 
-func (c *config) Build() (method.Method, error) {
+func (c *methodConfig) Build() (method.Method, error) {
 	return new(unenc), nil
 }
 
@@ -41,3 +42,7 @@ func Is(m method.Method) bool {
 	_, ok := m.(*unenc)
 	return ok
 }
+
+func IsConfig(m config.MethodConfig) bool {
+	return m.Type == "unencrypted"
+}