init bucketmeta struct

ecstore/src/bucket/lifecycle/transition.rs

@@ -0,0 +1,15 @@
+use time::OffsetDateTime;
+
+pub type TransitionDays = usize;
+
+#[derive(Debug)]
+pub struct TransitionDate(OffsetDateTime);
+
+#[derive(Debug)]
+pub struct Transition {
+    pub days: Option<TransitionDays>,
+    pub date: Option<TransitionDate>,
+    pub storage_class: String,
+
+    pub set: bool,
+}