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/models/upgrader/upgrade.rb

@@ -0,0 +1,27 @@
+class Upgrader::Upgrade
+  attr_reader :type, :commit_sha, :version, :url
+
+  def initialize(type, data)
+    @type = %w[release commit].include?(type) ? type : raise(ArgumentError, "Type must be either 'release' or 'commit'")
+    @commit_sha = data[:commit_sha]
+    @version = normalize_version(data[:version])
+    @url = data[:url]
+  end
+
+  def complete?
+    commit_sha == Maybe.commit_sha
+  end
+
+  def available?
+    version > Maybe.version || (version == Maybe.version && commit_sha != Maybe.commit_sha)
+  end
+
+  def to_s
+    type == "release" ? version.to_release_tag : "#{commit_sha.first(7)} (pre-release)"
+  end
+
+  private
+    def normalize_version(version)
+      version.is_a?(Semver) ? version : Semver.new(version)
+    end
+end