plancontext: use helpers to determine if CUE value is secret/fs/service

Signed-off-by: Andrea Luzzardi <aluzzardi@gmail.com>

plancontext/fs.go

@@ -18,6 +18,10 @@ var (
 	)
 )
 
+func IsFSValue(v *compiler.Value) bool {
+	return v.LookupPath(fsIDPath).Exists()
+}
+
 type FS struct {
 	id     string
 	result bkgw.Reference
@@ -54,10 +58,6 @@ func (c *fsContext) New(result bkgw.Reference) *FS {
 	return fs
 }
 
-func (c *fsContext) Contains(v *compiler.Value) bool {
-	return v.LookupPath(fsIDPath).Exists()
-}
-
 func (c *fsContext) FromValue(v *compiler.Value) (*FS, error) {
 	c.l.RLock()
 	defer c.l.RUnlock()