FIX: Consider webp a supported image format for upload (#9015)

* Also fixes an issue where if webp was a downloaded hotlinked
  image and then secure + sent in an email, it was not being
  redacted because webp was not a supported media format in
  FileHelper
* Webp originally removed as an image format in
  https://github.com/discourse/discourse/pull/6377
  and there was a spec to make sure a .bin webp
  file did not get renamed from its type to webp.

  However we want to support webp images now to make
  sure they are properly redacted if secure media is
  on, so change the example in the spec to use tiff,
  another banned format, instead

app/assets/javascripts/discourse/lib/uploads.js.es6

@@ -194,7 +194,7 @@ export function authorizesOneOrMoreImageExtensions(staff) {
 }
 
 export function isImage(path) {
-  return /\.(png|jpe?g|gif|svg|ico)$/i.test(path);
+  return /\.(png|webp|jpe?g|gif|svg|ico)$/i.test(path);
 }
 
 export function isVideo(path) {

lib/file_helper.rb

@@ -133,7 +133,7 @@ class FileHelper
   end
 
   def self.supported_images
-    @@supported_images ||= Set.new %w{jpg jpeg png gif svg ico}
+    @@supported_images ||= Set.new %w{jpg jpeg png gif svg ico webp}
   end
 
   def self.supported_audio

spec/lib/upload_creator_spec.rb

@@ -79,12 +79,12 @@ RSpec.describe UploadCreator do
         expect(upload.original_filename).to eq('png_as.png')
       end
 
-      describe 'for webp format' do
+      describe 'for tiff format' do
         before do
-          SiteSetting.authorized_extensions = '.webp|.bin'
+          SiteSetting.authorized_extensions = '.tiff|.bin'
         end
 
-        let(:filename) { "webp_as.bin" }
+        let(:filename) { "tiff_as.bin" }
         let(:file) { file_from_fixtures(filename) }
 
         it 'should not correct the coerce filename' do
@@ -96,7 +96,7 @@ RSpec.describe UploadCreator do
 
           expect(upload.extension).to eq('bin')
           expect(File.extname(upload.url)).to eq('.bin')
-          expect(upload.original_filename).to eq('webp_as.bin')
+          expect(upload.original_filename).to eq('tiff_as.bin')
         end
       end
     end

test/javascripts/lib/uploads-test.js.es6

@@ -123,7 +123,7 @@ QUnit.test("allows valid uploads to go through", assert => {
 });
 
 QUnit.test("isImage", assert => {
-  ["png", "jpg", "jpeg", "gif", "ico"].forEach(extension => {
+  ["png", "webp", "jpg", "jpeg", "gif", "ico"].forEach(extension => {
     var image = "image." + extension;
     assert.ok(isImage(image), image + " is recognized as an image");
     assert.ok(