Add web app model, service to fetch metadata

app/models/app_catalog.rb

@@ -0,0 +1,5 @@
+module AppCatalog
+  def self.table_name_prefix
+    "app_catalog_"
+  end
+end

app/models/app_catalog/web_app.rb

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+class AppCatalog::WebApp < ApplicationRecord
+
+  store :metadata, coder: JSON
+
+  validates :url, presence: true, uniqueness: true
+  validates :url, format: { with: URI.regexp },
+                  if: Proc.new { |a| a.url.present? }
+
+end

app/services/app_catalog_manager/fetch_metadata.rb

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+require 'manifique'
+
+module AppCatalogManager
+  class FetchMetadata < AppCatalogManagerService
+    def initialize(app)
+      @app = app
+    end
+
+    def call
+      agent = Manifique::Agent.new(url: @app.url)
+      metadata = agent.fetch_metadata
+
+      @app.name = metadata.name
+
+      [:name, :short_name, :description, :theme_color, :background_color,
+       :display, :start_url, :scope, :share_target].each do |prop|
+        @app.metadata[prop] = metadata.send(prop) if prop
+      end
+    rescue Manifique::Error => e
+      msg = "Fetching web app manifest failed for #{e.url}: #{e.type}"
+      Rails.logger.warn(msg)
+      Sentry.capture_message(msg) if Setting.sentry_enabled?
+      false
+    end
+  end
+end

app/services/app_catalog_manager_service.rb

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+class AppCatalogManagerService < ApplicationService
+end