Add email subscriptions (#38163)

app/controllers/api/v1/accounts/email_subscriptions_controller.rb

@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+class Api::V1::Accounts::EmailSubscriptionsController < Api::BaseController
+  before_action :set_account
+  before_action :require_feature_enabled!
+  before_action :require_account_permissions!
+
+  def create
+    @account.email_subscriptions.create!(email: params[:email], locale: I18n.locale)
+    render_empty
+  end
+
+  private
+
+  def set_account
+    @account = Account.local.find(params[:account_id])
+  end
+
+  def require_feature_enabled!
+    head 404 unless Mastodon::Feature.email_subscriptions_enabled?
+  end
+
+  def require_account_permissions!
+    head 404 if @account.unavailable? || !@account.user_can?(:manage_email_subscriptions) || !@account.user_email_subscriptions_enabled?
+  end
+end