Secret implementation of config. Supporting config merge (#2027)

Co-authored-by: Asim Aslam <asim@aslam.me>

config/config.go

@@ -27,16 +27,17 @@ type Value interface {
 }
 
 type Options struct {
-	// Is the value being read a secret?
-	// If true, the Config will try to decode it with `SecretKey`
 	Secret bool
 }
 
-// Option sets values in Options
 type Option func(o *Options)
 
-func Secret(isSecret bool) Option {
+func Secret(b bool) Option {
 	return func(o *Options) {
-		o.Secret = isSecret
+		o.Secret = b
 	}
 }
+
+type Secrets interface {
+	Config
+}