FEATURE: Support [description|attachment](upload://<short-sha>) in MD take 2.

Previous attempt was missing `post_uploads` records.

test/javascripts/lib/upload-short-url-test.js.es6

@@ -0,0 +1,81 @@
+import {
+  lookupCachedUploadUrl,
+  resolveAllShortUrls,
+  resetCache
+} from "pretty-text/upload-short-url";
+import { ajax } from "discourse/lib/ajax";
+
+QUnit.module("lib:pretty-text/upload-short-url", {
+  beforeEach() {
+    const response = object => {
+      return [200, { "Content-Type": "application/json" }, object];
+    };
+
+    const imageSrcs = [
+      {
+        short_url: "upload://a.jpeg",
+        url: "/uploads/default/original/3X/c/b/1.jpeg",
+        short_path: "/uploads/short-url/a.jpeg"
+      },
+      {
+        short_url: "upload://b.jpeg",
+        url: "/uploads/default/original/3X/c/b/2.jpeg",
+        short_path: "/uploads/short-url/b.jpeg"
+      }
+    ];
+
+    const attachmentSrcs = [
+      {
+        short_url: "upload://c.pdf",
+        url: "/uploads/default/original/3X/c/b/3.pdf",
+        short_path: "/uploads/short-url/c.pdf"
+      }
+    ];
+
+    // prettier-ignore
+    server.post("/uploads/lookup-urls", () => { //eslint-disable-line
+      return response(imageSrcs.concat(attachmentSrcs));
+    });
+
+    fixture().html(
+      imageSrcs.map(src => `<img data-orig-src="${src.url}">`).join("") +
+        attachmentSrcs.map(src => `<a data-orig-href="${src.url}">`).join("")
+    );
+  },
+
+  afterEach() {
+    resetCache();
+  }
+});
+
+QUnit.test("resolveAllShortUrls", async assert => {
+  let lookup;
+
+  lookup = lookupCachedUploadUrl("upload://a.jpeg");
+  assert.deepEqual(lookup, {});
+
+  await resolveAllShortUrls(ajax);
+
+  lookup = lookupCachedUploadUrl("upload://a.jpeg");
+
+  assert.deepEqual(lookup, {
+    url: "/uploads/default/original/3X/c/b/1.jpeg",
+    short_path: "/uploads/short-url/a.jpeg"
+  });
+
+  lookup = lookupCachedUploadUrl("upload://b.jpeg");
+
+  assert.deepEqual(lookup, {
+    url: "/uploads/default/original/3X/c/b/2.jpeg",
+    short_path: "/uploads/short-url/b.jpeg"
+  });
+
+  lookup = lookupCachedUploadUrl("upload://c.jpeg");
+  assert.deepEqual(lookup, {});
+
+  lookup = lookupCachedUploadUrl("upload://c.pdf");
+  assert.deepEqual(lookup, {
+    url: "/uploads/default/original/3X/c/b/3.pdf",
+    short_path: "/uploads/short-url/c.pdf"
+  });
+});