Add config description

lib/good_job.rb

@@ -17,7 +17,13 @@
 #
 # +GoodJob+ is the top-level namespace and exposes configuration attributes.
 module GoodJob
-  # TODO: explain me
+  # @!attribute [rw] active_record_parent_class
+  #   @!scope class
+  #   The ActiveRecord parent class inherited by +GoodJob::Job+ (default: +ActiveRecord::Base+).
+  #   Use this when using multiple databases or other custom ActiveRecord configuration.
+  #   @return [ActiveRecord::Base]
+  #   @example Change the base class:
+  #     GoodJob.active_record_parent_class = "CustomApplicationRecord"
   mattr_accessor :active_record_parent_class, default: "ActiveRecord::Base"
 
   # @!attribute [rw] logger

lib/good_job/lockable.rb

@@ -143,7 +143,7 @@ def with_advisory_lock
       def supports_cte_materialization_specifiers?
         return @_supports_cte_materialization_specifiers if defined?(@_supports_cte_materialization_specifiers)
 
-        @_supports_cte_materialization_specifiers = Job.connection.postgresql_version >= 120000
+        @_supports_cte_materialization_specifiers = connection.postgresql_version >= 120000
       end
     end
 
@@ -158,7 +158,7 @@ def advisory_lock
         WHERE pg_try_advisory_lock(('x'||substr(md5($1 || $2::text), 1, 16))::bit(64)::bigint)
       SQL
       binds = [[nil, self.class.table_name], [nil, send(self.class.primary_key)]]
-      Job.connection.exec_query(pg_or_jdbc_query(query), 'GoodJob::Lockable Advisory Lock', binds).any?
+      self.class.connection.exec_query(pg_or_jdbc_query(query), 'GoodJob::Lockable Advisory Lock', binds).any?
     end
 
     # Releases an advisory lock on this record if it is locked by this database