TUS: fix parallel uploads of the same file

## Issue
If you make 2 claims from the same source file, the second upload thinks it's trying to resume from the first one. They should be unique uploads.

## Approach
Stash the upload url for comparison when looking up existing uploads to resume.

Stash that in `params` to minimize code changes. We'll just need to ensure it is cleared before we generate the SDK payload.

flow-typed/publish.js

@@ -62,6 +62,8 @@ declare type FileUploadSdkParams = {
   remote_url?: string,
   thumbnail_url?: string,
   title?: string,
+  // Temporary values
+  uploadUrl?: string,
 };
 
 declare type FileUploadItem = {

ui/redux/reducers/publish.js

@@ -164,6 +164,12 @@ export const publishReducer = handleActions(
       if (progress) {
         currentUploads[key].progress = progress;
         delete currentUploads[key].status;
+
+        if (currentUploads[key].uploader.url && !currentUploads[key].params.uploadUrl) {
+          // TUS has finally obtained an upload url from the server. Stash that to check later when resuming.
+          // Ignoring immutable-update requirement (probably doesn't matter to the GUI).
+          currentUploads[key].params.uploadUrl = currentUploads[key].uploader.url;
+        }
       } else if (status) {
         currentUploads[key].status = status;
         if (status === 'error') {

web/setup/publish-v2.js

@@ -23,10 +23,13 @@ export function makeResumableUploadRequest(
       reject(new Error('Publish: v2 does not support remote_url'));
     }
 
+    const payloadParams = Object.assign({}, params);
+    delete payloadParams.uploadUrl; // cleanup
+
     const jsonPayload = JSON.stringify({
       jsonrpc: '2.0',
       method: RESUMABLE_ENDPOINT_METHOD,
-      params,
+      params: payloadParams,
       id: new Date().getTime(),
     });
 
@@ -92,8 +95,9 @@ export function makeResumableUploadRequest(
     uploader
       .findPreviousUploads()
       .then((previousUploads) => {
-        if (previousUploads.length > 0) {
-          uploader.resumeFromPreviousUpload(previousUploads[0]);
+        const index = previousUploads.findIndex((prev) => prev.uploadUrl === params.uploadUrl);
+        if (index !== -1) {
+          uploader.resumeFromPreviousUpload(previousUploads[index]);
         }
 
         if (!isPreview) {