setPeek(true) is not honored when getting an inner imap message part

[gbulfon]

Describe the bug
While setPeek(true) works fine on an IMAPMessage when getting content data such as text parts or attachment parts, when trying to get the content of an inner message part (an attached eml) the message changes to the seen state.
This has been verified to happen both on a Cyrus and Dovecot imap server.

To Reproduce
Steps to reproduce the behavior:

1. get an unseen IMAPMessage instance from an IMAPFolder as m.
2. m.setPeek(true)
3. get the eml attachment part from the message as p.
4. (Message)p.getContent() and use it

Expected behavior
The original message should be still in the unseen state

Mail server:

• Protocol being used: imap
• Vendor/product: Cyrus/Dovecot

Additional context
We're using jakarta-mail 2.0.0