Testimonial sharing email should only show new testimonials shared

[BradHN1]

User Story.
As a community admin
I want to receive an email with just the new testimonials
So that I can review just the ones I need to to make sure they are ok

Additional details/context
As a cadmin of cooler concord, I receive an email once a week with the same shared testimonila listed. This is not useful since I've already reviewed the testimonial and accepted it.

For the new web platform we need to ensure that emails like this are useful and actionable. If it is not usefuo it seems like spam to be ignored

Value added.
What do you think the value of adding this feature is? Help managers and developers know how this should be prioritized.

Acceptance criteria.
The conditions that must be met for this to be done. For example, for a login feature: User is securely and reliably logged in until timeout or manual sign-out.