Add REST API for creating an account (#9572)

* Add REST API for creating an account

The method is available to apps with a token obtained via the client
credentials grant. It creates a user and account records, as well as
an access token for the app that initiated the request. The user is
unconfirmed, and an e-mail is sent as usual.

The method returns the access token, which the app should save for
later. The REST API is not available to users with unconfirmed
accounts, so the app must be smart to wait for the user to click a
link in their e-mail inbox.

The method is rate-limited by IP to 5 requests per 30 minutes.

* Redirect users back to app from confirmation if they were created with an app

* Add tests

* Return 403 on the method if registrations are not open

* Require agreement param to be true in the API when creating an account

3 files changed, 6 insertions, 1 deletions

diff --git a/config/initializers/rack_attack.rb b/config/initializers/rack_attack.rb
index 8756b8fbf..35302e37b 100644
--- a/config/initializers/rack_attack.rb
+++ b/config/initializers/rack_attack.rb
@@ -57,6 +57,10 @@ class Rack::Attack
     req.authenticated_user_id if req.post? && req.path.start_with?('/api/v1/media')
   end
 
+  throttle('throttle_api_sign_up', limit: 5, period: 30.minutes) do |req|
+    req.ip if req.post? && req.path == '/api/v1/accounts'
+  end
+
   throttle('protected_paths', limit: 25, period: 5.minutes) do |req|
     req.ip if req.post? && req.path =~ PROTECTED_PATHS_REGEX
   end
diff --git a/config/locales/devise.en.yml b/config/locales/devise.en.yml
index 20938e47b..bd0642b25 100644
--- a/config/locales/devise.en.yml
+++ b/config/locales/devise.en.yml
@@ -18,6 +18,7 @@ en:
     mailer:
       confirmation_instructions:
         action: Verify email address
+        action_with_app: Confirm and return to %{app}
         explanation: You have created an account on %{host} with this email address. You are one click away from activating it. If this wasn't you, please ignore this email.
         extra_html: Please also check out <a href="%{terms_path}">the rules of the instance</a> and <a href="%{policy_path}">our terms of service</a>.
         subject: 'Mastodon: Confirmation instructions for %{instance}'
diff --git a/config/routes.rb b/config/routes.rb
index 7723a08af..808bb5acd 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -336,7 +336,7 @@ Rails.application.routes.draw do
         resources :relationships, only: :index
       end
 
-      resources :accounts, only: [:show] do
+      resources :accounts, only: [:create, :show] do
         resources :statuses, only: :index, controller: 'accounts/statuses'
         resources :followers, only: :index, controller: 'accounts/follower_accounts'
         resources :following, only: :index, controller: 'accounts/following_accounts'