Revert "Allow a Message to be decomposed into a MessageBuilder (#633)" (#649)
Revert "Allow a Message to be decomposed into a MessageBuilder (#633)" (#649)

This reverts commit aadcc0f83cbd752e1089d1611aa4414e4f9d9981.

Co-authored-by: Alexis Mousset <1a73af9e7ae00182733b2292511b814be66f065f@amousset.me>
lettre/lettre,amousset/lettre,amousset/lettre