Invoke headers function for remote uploads (#4596)

Invoke headers function for remote uploads

packages/@uppy/aws-s3/src/index.js

@@ -276,7 +276,7 @@ export default class AwsS3 extends UploaderPlugin {
       metadata: Object.fromEntries(allowedMetaFields.map(name => [name, file.meta[name]])),
       httpMethod: opts.method,
       useFormData: opts.formData,
-      headers: opts.headers,
+      headers: typeof opts.headers === 'function' ? opts.headers(file) : opts.headers,
     })
     return res.token
   }

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

@@ -447,7 +447,7 @@ export default class Tus extends UploaderPlugin {
       uploadUrl: opts.uploadUrl,
       protocol: 'tus',
       size: file.data.size,
-      headers: opts.headers,
+      headers: (typeof opts.headers === 'function') ? opts.headers(file) : opts.headers,
       metadata: file.meta,
     }, options)
     return res.token

packages/@uppy/xhr-upload/src/index.js

@@ -366,7 +366,7 @@ export default class XHRUpload extends UploaderPlugin {
       metadata: Object.fromEntries(allowedMetaFields.map(name => [name, file.meta[name]])),
       httpMethod: opts.method,
       useFormData: opts.formData,
-      headers: opts.headers,
+      headers: typeof opts.headers === 'function' ? opts.headers(file) : opts.headers,
     }, options)
     return res.token
   }