Merge branch 'master' into glitch-soc/merge-upstream

Conflicts:
- `README.md`:
  Our README.md files are completely different. Discarded upstream changes.
- `app/javascript/core/admin.js`:
  Updating rails-ujs, no real conflict, but a comment to close to changed
  code. Various glitch-soc-only files have been updated to match those changes,
  though.
- `package.json`:
  No real conflict, just an additional dependency in glitch-soc that was too
  close to something updated upstream. Took upstream's changes.

app/controllers/api/v2/media_controller.rb

@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+class Api::V2::MediaController < Api::V1::MediaController
+  def create
+    @media_attachment = current_account.media_attachments.create!({ delay_processing: true }.merge(media_attachment_params))
+    render json: @media_attachment, serializer: REST::MediaAttachmentSerializer, status: 202
+  rescue Paperclip::Errors::NotIdentifiedByImageMagickError
+    render json: file_type_error, status: 422
+  rescue Paperclip::Error
+    render json: processing_error, status: 500
+  end
+end