resolve_hash_connection

# File activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 42
        def resolve_hash_connection(spec) # :nodoc:
          spec = spec.symbolize_keys

          raise(AdapterNotSpecified, "database configuration does not specify adapter") unless spec.key?(:adapter)

          begin
            require "active_record/connection_adapters/#{spec[:adapter]}_adapter"
          rescue LoadError => e
            raise LoadError, "Please install the #{spec[:adapter]} adapter: `gem install activerecord-#{spec[:adapter]}-adapter` (#{e.message})", e.backtrace
          end

          adapter_method = "#{spec[:adapter]}_connection"

          ConnectionSpecification.new(spec, adapter_method)
        end