Adding support to define the headers as a function in the Tus protocol plugin

packages/@uppy/tus/src/index.js

@@ -185,6 +185,10 @@ module.exports = class Tus extends BasePlugin {
         ...(file.tus || {}),
       }
 
+      if (typeof opts.headers === 'function') {
+        opts.headers = opts.headers(file)
+      }
+
       /** @type {RawTusOptions} */
       const uploadOptions = {
         ...tusDefaultOptions,

website/src/docs/tus.md

@@ -47,7 +47,25 @@ Destination URL for your uploads. This should be where your tus.io server is run
 
 ### `headers: {}`
 
-Additional request headers to send to the Tus endpoint when making requests.
+An object containing additional HTTP headers to send to the Tus endpoint when making requests.
+Keys are header names, values are header values.
+
+```js
+const headers = {
+  authorization: `Bearer ${window.getCurrentUserToken()}`,
+}
+```
+
+Header values can also be derived from file data by providing a function. The function receives a [File Object][File Objects] and must return an object where the keys are header names, and values are header values.
+
+```js
+const headers = (file) => {
+  return {
+    authorization: `Bearer ${window.getCurrentUserToken()}`,
+    expires: file.meta.expires,
+  }
+}
+```
 
 ### `chunkSize: Infinity`
 
@@ -80,3 +98,5 @@ Pass an array of field names to limit the metadata fields that will be added to
 Limit the amount of uploads going on at the same time. Setting this to `0` means there is no limit on concurrent uploads.
 
 [tus-js-client]: https://github.com/tus/tus-js-client
+
+[File Objects]: /docs/uppy/#File-Objects