I've built a first pass at this in https://github.com/cuny-academic-commons/cac/commit/1dd34cac929b7c1e44094f4924fe170020929927.
For the time being, the subject line is: "More information about your Commons Teaching [Site/Group]". Happy to adjust this as others see fit.
In the case of a Group + Site, only the group creation triggers an email.
Once we've gotten close with testing on the News page redesign #16535, I'll be able to share this on cdev for testing.
For internal reference, the CLI commands I used to set up the email (be sure to change the ID in the last line):
wp term create bp-email-type teaching_space_reminder --slug=teaching_space_reminder --description="An instructor has created a Teaching space on the Commons"
wp post create --post_type=bp-email --post_title="Inviting Students to your Course on the Commons" --post_status=publish --post_content='<p>Dear Faculty Member,</p>
<p>It’s great to see that you have created another “Teaching” {{{cac.teachingItemType}}} on the Commons! Once you have set up your course you may want to add students so they can engage with you and their peers on the course. Please note, if your site will be visible only to Commons users, or users who join your {{{cac.teachingItemType}}} students will have to join the Commons to see your course.</p>
<p>This email will provide a quick refresher and helpful links for inviting students to the Commons and adding them to your {{{cac.teachingItemType}}}.</p>
<p>To invite students to your course:</p>
<ol>
<li>If you have a Group, click Send Invites in the gray menu bar on the left.</li>
<li>If you have a Site, in the Dashboard, click Users > Add New.</li>
<li>If you have a Connected Group/Site, make sure the roles are synced. Invite students to the group (Option 1, above) and they will be automatically added to the site.</li>
</ol>
<p>Following the steps above, when you go through the process to invite students you will encounter the “Invitation Portal”. In this portal, you can invite students using their CUNY email address (one per line).</p>
<p>Inviting students to your {{{cac.teachingItemType}}} will prompt the student to join the Commons if they are not already a user. Once the student signs up for the Commons using their CUNY email, they will have an invitation to join your course {{{cac.teachingItemType}}}.</p>
More detailed steps for inviting students to the Commons: <a href="https://help.commons.gc.cuny.edu/inviting-students-to-the-commons/">Inviting Students to the Commons</a>.
Students can also register for the Commons on their own, and then search for your course {{{cac.teachingItemType}}} in <a href="https://commons.gc.cuny.edu/courses/">the course directory</a> and request to join.
<p><u><b>Helpful Links to Share with Students</b></u></p>
<ul>
<li><a href="https://help.commons.gc.cuny.edu/getting-started-with-the-commons/">How do I join the Commons?</a></li>
<li><a href="https://help.commons.gc.cuny.edu/cuny-email-addresses/">What is my CUNY email address?</a></li>
<li><a href="https://help.commons.gc.cuny.edu/my/">How can I find my course on the Commons?</a></li>
</ul>
<p>If you have questions about inviting students to the Commons, or other questions about teaching on the Commons, please reach out to the Commons HELP desk: support@cunycommons.zendesk.com.</p>'
wp post term set 28957 bp-email-type teaching_space_reminder