New buckets for 0.6.0: small changes

- Fix bucket delete

- fix merge of bucket creation date

- Replace deletable with option in aliases
    Rationale: if two aliases point to conflicting bucket, resolving
    by making an arbitrary choice risks making data accessible when it
    shouldn't be. We'd rather resolve to deleting the alias until
    someone puts it back.

src/model/bucket_alias_table.rs

@@ -10,32 +10,23 @@ use garage_table::*;
 #[derive(PartialEq, Clone, Debug, Serialize, Deserialize)]
 pub struct BucketAlias {
 	name: String,
-	pub state: crdt::Lww<crdt::Deletable<AliasParams>>,
-}
-
-#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Debug, Serialize, Deserialize)]
-pub struct AliasParams {
-	pub bucket_id: Uuid,
-}
-
-impl AutoCrdt for AliasParams {
-	const WARN_IF_DIFFERENT: bool = true;
+	pub state: crdt::Lww<Option<Uuid>>,
 }
 
 impl BucketAlias {
-	pub fn new(name: String, ts: u64, bucket_id: Uuid) -> Option<Self> {
+	pub fn new(name: String, ts: u64, bucket_id: Option<Uuid>) -> Option<Self> {
 		if !is_valid_bucket_name(&name) {
 			None
 		} else {
 			Some(BucketAlias {
 				name,
-				state: crdt::Lww::raw(ts, crdt::Deletable::present(AliasParams { bucket_id })),
+				state: crdt::Lww::raw(ts, bucket_id),
 			})
 		}
 	}
 
 	pub fn is_deleted(&self) -> bool {
-		self.state.get().is_deleted()
+		self.state.get().is_none()
 	}
 	pub fn name(&self) -> &str {
 		&self.name