Display bcc line to bcc recipient

**Is your feature request related to a problem? Please describe.**
When a bcc recipient receives a message it shows the To and CC header lines but does not include a BCC line indicating that they are a BCC recipient. This behavior seems different from most email clients which do display the BCC line to _that_ BCC recipient only. So, not displaying the bcc header can cause some confusion to an email user.

**Describe the solution you'd like**
It would be nice to include a BCC line indicating the BCC recipient's address to that BCC recipient, only.

**Describe alternatives you've considered**
None.

**Additional context**
From: John Doe
To: Jane Smith
Bcc: Me

Start in the Jakarta Mail API specification repository by reviewing the existing message-header behavior described in the issue and its From/To/Bcc example. Done means a BCC recipient sees a BCC line containing that recipient's address, while other recipients do not see it; no specific file or test is named.

Written by the indexing model from the issue text.