cannot find content in Trans for on-screen join congrats message on Members tab

Look at http://next.dev.curriki.org/xwiki/bin/view/Group_CSPLCMOPENPUBLIC/JoinGroup and join the group.

Note the text displayed there:

1) The header bar reads: JOIN THIS GROUP

2) The messages reads: Join Congratulations! You have successfully joined this group. You can no navigate to the Group home page.

FIX:

I would like to edit both of these so that the header bar reads: "CONGRATULATIONS ON JOINING THIS GROUP!"

and so that the message reads: "You have successfully joined this group."

And I would like to be able to control this in the Trans going forward.