Security Tracker Emails: Strip the Body Field Or Encrypt with Recipient's Pubic GPG Key

This issue was spun off from #2344581: [META] Securing Security Team Communications and Conversations → (see comments #4 through #15). The goal is to not disclose sensitive information over email in an unencrypted form. The proposal in #8 on the parent issue was discussed as an agreeable solution. In essence, a security team member would either:

1. Upload their public GPG key to their profile, which would be used to encrypt the body/description field.
2. If a key is not present, strip the body/description field out of the email altogether.

@killes was mentioned to be working on this, hence the desire to split off a second ticket so that we could track that progress and provide assistance.