Reuse recent CDN locators

ts/sql/Interface.std.ts

@@ -804,6 +804,16 @@ strictAssert(
   'attachment_columns must match DB fields type'
 );
 
+export type ExistingAttachmentUploadData = {
+  cdnKey: string;
+  cdnNumber: number;
+  digest: string;
+  key: string;
+  uploadTimestamp: number;
+  incrementalMac: string | null;
+  chunkSize: number | null;
+};
+
 export type ExistingAttachmentData = Pick<
   MessageAttachmentDBType,
   | 'version'
@@ -1085,6 +1095,10 @@ type ReadableInterface = {
     version: number
   ) => Array<MessageAttributesType>;
 
+  getMostRecentAttachmentUploadData: (
+    plaintextHash: string
+  ) => ExistingAttachmentUploadData | undefined;
+
   __dangerouslyRunAbitraryReadOnlySqlQuery: (
     readOnlySqlQuery: string
   ) => ReadonlyArray<RowType<object>>;