Quietly fail init if no database is present

Failing loudly under these circs context isn't helpful because it
doesn't reflect a problem with the analytics setup; apps in CI often run
the asset precompilation step without a database present.

lib/dfe/analytics.rb

@@ -79,6 +79,13 @@ def self.configure
     end
 
     def self.initialize!
+      begin
+        ActiveRecord::Base.connection
+      rescue ActiveRecord::ActiveRecordError
+        Rails.logger.info('No database connection; DfE Analytics not initialized')
+        return
+      end
+
       DfE::Analytics::Fields.check!
 
       entities_for_analytics.each do |entity|

spec/dfe/analytics_spec.rb

@@ -14,6 +14,14 @@
     end
   end
 
+  describe 'when no database connection is available' do
+    it 'recovers and logs' do
+      allow(ActiveRecord::Base).to receive(:connection).and_raise(ActiveRecord::ConnectionNotEstablished)
+      allow(Rails.logger).to receive(:info).with(/No database connection/)
+      expect { DfE::Analytics.initialize! }.not_to raise_error
+    end
+  end
+
   describe 'field checks on initialization' do
     # field validity is computed from allowlist, blocklist and database. See
     # Analytics::Fields for more details