resolve_config_for_connection

# File activerecord/lib/active_record/connection_handling.rb, line 172
    def resolve_config_for_connection(config_or_env) # :nodoc:
      raise "Anonymous class is not allowed." unless name

      config_or_env ||= DEFAULT_ENV.call.to_sym
      pool_name = primary_class? ? "primary" : name
      self.connection_specification_name = pool_name

      resolver = ConnectionAdapters::ConnectionSpecification::Resolver.new(Base.configurations)
      config_hash = resolver.resolve(config_or_env, pool_name).symbolize_keys
      config_hash[:name] = pool_name

      config_hash
    end