Support remote follow request providing URL instead of acct

app/controllers/authorize_follow_controller.rb

@@ -6,7 +6,14 @@ class AuthorizeFollowController < ApplicationController
   before_action :authenticate_user!
 
   def new
-    @account = FollowRemoteAccountService.new.call(params[:acct])
+    uri = Addressable::URI.parse(params[:acct])
+
+    if uri.path && %w(http https).include?(uri.scheme)
+      set_account_from_url
+    else
+      set_account_from_acct
+    end
+
     render :error if @account.nil?
   end
 
@@ -21,4 +28,14 @@ class AuthorizeFollowController < ApplicationController
   rescue ActiveRecord::RecordNotFound, Mastodon::NotPermitted
     render :error
   end
+
+  private
+
+  def set_account_from_url
+    @account = FetchRemoteAccountService.new.call(params[:acct])
+  end
+
+  def set_account_from_acct
+    @account = FollowRemoteAccountService.new.call(params[:acct])
+  end
 end