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/upgrades_controller.rb

@@ -0,0 +1,56 @@
+class UpgradesController < ApplicationController
+  before_action :verify_upgrades_enabled
+
+  def acknowledge
+    commit_sha = params[:id]
+    upgrade = Upgrader.find_upgrade(commit_sha)
+
+    if upgrade
+      if upgrade.available?
+        Current.user.acknowledge_upgrade_prompt(upgrade.commit_sha)
+        flash[:notice] = t(".upgrade_dismissed")
+      elsif upgrade.complete?
+        Current.user.acknowledge_upgrade_alert(upgrade.commit_sha)
+        flash[:notice] = t(".upgrade_complete_dismiss")
+      else
+        flash[:alert] = t(".upgrade_not_available")
+      end
+    else
+      flash[:alert] = t(".upgrade_not_found")
+    end
+
+    redirect_back(fallback_location: root_path)
+  end
+
+  def deploy
+    commit_sha = params[:id]
+    upgrade = Upgrader.find_upgrade(commit_sha)
+
+    unless upgrade
+      flash[:alert] = t(".upgrade_not_found")
+      return redirect_back(fallback_location: root_path)
+    end
+
+    prior_acknowledged_upgrade_commit_sha = Current.user.last_prompted_upgrade_commit_sha
+
+    # Optimistically acknowledge the upgrade prompt
+    Current.user.acknowledge_upgrade_prompt(upgrade.commit_sha)
+
+    upgrade_result = Upgrader.upgrade_to(upgrade)
+
+    if upgrade_result[:success]
+      flash[:notice] = upgrade_result[:message]
+    else
+      # If the upgrade fails, revert to the prior acknowledged upgrade
+      Current.user.acknowledge_upgrade_prompt(prior_acknowledged_upgrade_commit_sha)
+      flash[:alert] = upgrade_result[:message]
+    end
+
+    redirect_back(fallback_location: root_path)
+  end
+
+  private
+    def verify_upgrades_enabled
+      head :not_found unless ENV["UPGRADES_ENABLED"] == "true"
+    end
+end