Support @ProtonMail web client apps stack v4.1.0+

[vladimiry]

@ProtonMail has recently deployed 4.1.0 WebClient at https://beta.protonmail.com. This version is a from-scratch rework and is now based on React rather than on AngularJS. So ElectronMail will need to significantly rework the integration layer.

Besides it now uses Single Sign-On scenario / SSO via the https://account.protonmail.com web app sources if which is not yet shared in protonmail organization.. The https://github.com/ProtonMail/proton-account project has been shared on request.

The goal is:

• To use/embed-in-the-app the protonmail web clients without their Single Sign-on / SSO thing but having the persisting session instead to work as it does in the current stable release.
• The persistent sessions feature should keep working as it does in the current stable release / v4.8.0. Protonmail enables its own persistent sessions functionality / SSO thing since v4.1.0+ release but ElectronMail keeps all the sensitive data protected by the master password, ie encrypted, whilst protonmail keeps some sensitive data in the browser's local storage which in general weakens the security.
• None of the existing functionality should be dropped.

Adopting a new https://github.com/ProtonMail/proton-account project is required since protonmail has moved there essential account-related options which were originally located in https://github.com/ProtonMail/proton-mail-settings project.

[vladimiry]

I've been working on the task for a while and things go well so far.

The remaining things to convert to a new proto-mail-client are:

• support spell check in composing editor
• "view online" button in the local store view mode
• attachments export (feature enabled in v4.7.0)

After finishing conversion there will be a need to test the stability for a while, in action, and we are good then.

[vladimiry]

All the points have been handled in my TODO list for this task, so I believe a new release is going to happen next week.

[vladimiry]

I planned to release v4.9.0 this week but it appears that there is a major issue at the proton side which I'd prefer them to sort out before the new ElectronMail version gets on the rails. Not sharing issue details yet.

[vladimiry]

it appears that there is a major issue at the proton side which I'd prefer them to sort out before the new ElectronMail version gets on the rails

The issue has been reported to the company and confirmed just recently. The named ETA on fixing it is 2-3 weeks which is unfortunate. So v4.9.0 app release gets delayed for 2-3 weeks. I believe though there is still a chance it gets fixed earlier.

[vladimiry]

If someone will be assembling the installation package from sources before v4.9.0 released, I highly recommend enabling the opt-in Block non "API entry point"-based network requests option for all accounts (see how to enable it on the screenshot in #312 (comment)).

[vladimiry]

The issue has been reported to the company and confirmed just recently. The named ETA on fixing it is 2-3 weeks which is unfortunate.

The issue appears to be fixed now. The problem was that when the user was exporting the email message in Proton's UI via "More => Export" click all the inlined to email images were requested. So the export was not efficient since there is no need to request inlined images during exporting to EML. But more importantly, the IP address was silently leaking without the user's consent.

There is no blocker anymore and so the app v4.9.0 release is on the way.