Accept terms of service as part of new user sign up
Follow up https://gitlab.com/gitlab-org/gitlab-ce/issues/44798, so that you are already accepting the terms of service right when you sign up, as part of the sign up flow itself.
The design could be https://gitlab.com/gitlab-org/gitlab-ce/uploads/d198fb8fa2531edb4490f26be1f7b90e/Screen_Shot_2018-04-11_at_11.51.56_AM.png, as sketched out in https://gitlab.com/gitlab-org/gitlab-ce/issues/44798#note_67951389.
With this feature, the user wouldn't see the modal right after they sign up, because they've already accepted as part of new user sign up, (and so that db flag would already be set).