Add protocol handler. Handle follow intents (#4511)

* Add protocol handler. Handle follow intents

* Add share intent

* Improve code in intents controller

* Adjust share form CSS

app/controllers/shares_controller.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+class SharesController < ApplicationController
+  layout 'public'
+
+  before_action :authenticate_user!
+
+  def show
+    serializable_resource = ActiveModelSerializers::SerializableResource.new(InitialStatePresenter.new(initial_state_params), serializer: InitialStateSerializer)
+    @initial_state_json   = serializable_resource.to_json
+  end
+
+  private
+
+  def initial_state_params
+    {
+      settings: Web::Setting.find_by(user: current_user)&.data || {},
+      push_subscription: current_account.user.web_push_subscription(current_session),
+      current_account: current_account,
+      token: current_session.token,
+      admin: Account.find_local(Setting.site_contact_username),
+      text: params[:text],
+    }
+  end
+end