The Proton-API-Bridge should not be attempting to take over, nor
re-define, the existing proton-go-api interfaces. This is known has an
"unfriendly fork" and increases the overall complexity of maintaining
the Proton-API-Bridge.
All changes to the proton-go-api should be done as "friendly" as
possible, and should be submitted back upstream for inclusion. This
improves the functionality of the proton-go-api for more than just 1
project, and it reduces the long-term maintenance required for
Proton-API-Bridge.
To this end, Proton-API-Bridge should be written to always assume it is
using github.com/ProtonMail/proton-go-api and leverage the `replace`
operation in go.mod in order to leverage our "friendly fork" of
proton-go-api. I.e. the long-term goal should be to _not_ maintain a
fork of proton-go-api.
> Anything else would be uncivilized.
Add config option - ReplaceExistingDraft
Refactor and add integration tests
Update README and add notes for MIME parsing and progress bug
Improve returned errors
