Add zero-config self hosting on Render (#612)

* v1 of backend implementation for self hosting

* Add docs

* Add upgrades controller

* Add global helpers for self hosting mode

* Add self host settings controller

* Conditionally show self hosting settings

* Environment and config updates

* Complete upgrade prompting flow

* Update config for forked repo

* Move configuration of github provider within class

* Add upgrades cron

* Update deploy button

* Update guides

* Fix render deployer

* Typo

* Enable auto upgrades

* Fix cron

* Make upgrade modes more clear and consistent

* Trigger new available version

* Fix logic for displaying upgrade prompts

* Finish implementation

* Fix regression

* Trigger new version

* Add i18n translations

* trigger new version

* reduce caching time for testing

* Decrease cache for testing

* trigger upgrade

* trigger upgrade

* Only trigger deploy once

* trigger upgrade

* If target is commit, always upgrade if any upgrade is available

* trigger upgrade

* trigger upgrade

* Test release

* Change back to maybe repo for defaults

* Fix lint errors

* Clearer naming

* Fix relative link

* Add abs path

* Relative link

* Update docs

app/controllers/settings/self_hosting_controller.rb

@@ -0,0 +1,46 @@
+class Settings::SelfHostingController < ApplicationController
+  before_action :verify_self_hosting_enabled
+
+  def edit
+  end
+
+  def update
+    if all_updates_valid?
+      self_hosting_params.keys.each do |key|
+        Setting.send("#{key}=", self_hosting_params[key].strip)
+      end
+
+      redirect_to edit_settings_self_hosting_path, notice: t(".success")
+    else
+      flash.now[:error] = @errors.first.message
+      render :edit, status: :unprocessable_entity
+    end
+  end
+
+  private
+    def all_updates_valid?
+      @errors = ActiveModel::Errors.new(Setting)
+      self_hosting_params.keys.each do |key|
+        setting = Setting.new(var: key)
+        setting.value = self_hosting_params[key].strip
+
+        unless setting.valid?
+          @errors.merge!(setting.errors)
+        end
+      end
+
+      if self_hosting_params[:upgrades_mode] == "auto" && self_hosting_params[:render_deploy_hook].blank?
+        @errors.add(:render_deploy_hook, t("settings.self_hosting.update.render_deploy_hook_error"))
+      end
+
+      @errors.empty?
+    end
+
+    def self_hosting_params
+      params.require(:setting).permit(:render_deploy_hook, :upgrades_mode, :upgrades_target)
+    end
+
+    def verify_self_hosting_enabled
+      head :not_found unless self_hosted?
+    end
+end