add uppy.logout() (#2850)

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

@@ -953,6 +953,14 @@ class Uppy {
     this.cancelAll()
   }
 
+  logout () {
+    this.iteratePlugins(plugin => {
+      if (plugin.provider && plugin.provider.logout) {
+        plugin.provider.logout()
+      }
+    })
+  }
+
   _calculateProgress (file, data) {
     if (!this.getFile(file.id)) {
       this.log(`Not setting progress for a file that has been removed: ${file.id}`)

website/src/docs/uppy.md

@@ -665,6 +665,10 @@ Stop all uploads in progress and clear file selection, set progress to 0. Basica
 
 Uninstall all plugins and close down this Uppy instance. Also runs `uppy.reset()` before uninstalling.
 
+### `uppy.logout()`
+
+Calls `provider.logout()` on each remote provider plugin (Google Drive, Instagram, etc). Useful, for example, after your users log out of their account in your app — this will clean things up with Uppy cloud providers as well, for extra security.
+
 ### `uppy.log()`
 
 #### Parameters