enable opt-in live attachments export feature

* the feature can only be used if the network connection is "online" and a user is "signed-in" into the email account since live attachments loading and decrypting will be happening (attachments not stored in the local database)

README.md

@@ -30,7 +30,7 @@ The way of verifying that the installation packages attached to the [releases](h
 - :gear: **Reproducible builds**.
 - :gear: **Cross platform**. The app works on Linux/OSX/Windows platforms.
 - :mag_right: **Full-text search**. Enabled with [v2.2.0](https:/vladimiry/ElectronMail/releases/tag/v2.2.0) release. See the respective [issue](https:/vladimiry/ElectronMail/issues/92) for details.
-- :package: **Offline access to the email messages** (only emails body content, not the attachments). The [local store](https://user-images.githubusercontent.com/1560781/51189497-382a6c00-18f1-11e9-9b9a-baa63f0c0ff4.gif) feature enables storing your messages in the encrypted `database.bin` file, so you could view your messages offline, perform a full-text search against them and export them to EML files. Enabled since [v2.0.0](https:/vladimiry/ElectronMail/releases/tag/v2.0.0) release. 
+- :package: **Offline access to the email messages** (only emails body content stored locally but not the attachments). The [local store](https://user-images.githubusercontent.com/1560781/51189497-382a6c00-18f1-11e9-9b9a-baa63f0c0ff4.gif) feature enables storing your messages in the encrypted `database.bin` file, so you could view your messages offline, perform a full-text search against them and export them to EML files. Enabled since [v2.0.0](https:/vladimiry/ElectronMail/releases/tag/v2.0.0) release. 
 - :mailbox: **Multi accounts** support per each email provider including supporting individual [entry point domains](https:/vladimiry/ElectronMail/issues/29).
 - :unlock: **Automatic login into the app** with a remembered master password using [keytar](https:/atom/node-keytar) module ([keep me signed in](images/keep-me-signed-in.png) feature).
 - :unlock: **Automatic login into the email accounts**, including filling [2FA tokens](https:/vladimiry/ElectronMail/issues/10). Two auto-login delay scenarios supported in order to make it harder to correlate the identities, see the respective [issue](https:/vladimiry/ElectronMail/issues/121).
@@ -41,8 +41,8 @@ The way of verifying that the installation packages attached to the [releases](h
 - :gear: **Starting minimized to tray**.
 - :gear: **Closing to tray**.
 - :gear: **Switchable accounts handle buttons positioning** (`top` , `left`, `left-thin`). See details in [#36](https:/vladimiry/ElectronMail/issues/36) and [#175](https:/vladimiry/ElectronMail/issues/175). Demo screenshots placed in the [images](images) folder (specifically [this](images/controls-view-modes-(top-left-left_thing).gif) image).
-- :package: **Batch emails export** to EML files (only emails body content, not the attachments). Feature released with [v2.0.0-beta.4](https:/vladimiry/ElectronMail/releases/tag/v2.0.0-beta.4) version, requires `local messages store` feature to be enabled ([how to enable](https:/vladimiry/ElectronMail/releases/tag/v2.0.0-beta.1)).
-- :closed_lock_with_key: **Built-in/prepackaged web clients**. The built-in web clients are built from source code, see respective official [Protonmail](https:/ProtonMail/WebClient) repository. See [79](https:/vladimiry/ElectronMail/issues/79) and [80](https:/vladimiry/ElectronMail/issues/80) issues for details.
+- :package: **Batch emails export** to EML files (attachments can optionally be exported in online/live mode). Feature released with [v2.0.0-beta.4](https:/vladimiry/ElectronMail/releases/tag/v2.0.0-beta.4) version, requires `local messages store` feature to be enabled ([how to enable](https:/vladimiry/ElectronMail/releases/tag/v2.0.0-beta.1)).
+- :closed_lock_with_key: **Built-in/prepackaged web clients**. The prepackaged with the app proton web clients assembled from source code, see the respective [official repositories](https:/ProtonMail/). See [79](https:/vladimiry/ElectronMail/issues/79) and [80](https:/vladimiry/ElectronMail/issues/80) issues for details.
 - :gear: **Configuring proxy per account** support. Enabled since [v3.0.0](https:/vladimiry/ElectronMail/releases/tag/v3.0.0) release. See [113](https:/vladimiry/ElectronMail/issues/113) and [120](https:/vladimiry/ElectronMail/issues/120) issues for details.
 - :pencil: **Spell Checking**.
 

package.json

@@ -1,7 +1,7 @@
 {
  "name": "electron-mail",
  "description": "Unofficial ProtonMail Desktop App",
- "version": "4.6.1",
+ "version": "4.7.0",
  "author": "Vladimir Yakovlev <[email protected]>",
  "license": "MIT",
  "homepage": "https:/vladimiry/ElectronMail",

src/@types/globals.d.ts

@@ -1,4 +1,4 @@
-import {Observable, Subject} from "rxjs";
+import {Observable, Subject, Subscriber} from "rxjs";
 
 import {BuildEnvironment} from "webpack-configs/model";
 
@@ -13,10 +13,12 @@ declare global {
  T extends Promise<infer U2> ? U2 :
  T extends Observable<infer U3> ? U3 :
  T extends Subject<infer U3> ? U3 :
- T;
+ T extends Subscriber<infer U3> ? U3 :
+ T;
 
  type Mutable<T> = import("ts-essentials").Writable<T>;
 
+ // TODO add "DeepNoExtraProperties" type
  type NoExtraProperties<T, U extends T = T> = U & Impossible<Exclude<keyof U, keyof T>>;
 
  type StrictOmit<T, K extends keyof T> = import("ts-essentials").StrictOmit<T, K>;

src/electron-main/__test__/api/index.spec.ts

@@ -34,6 +34,7 @@ interface TestContext {
  | "applySavedProtonBackendSession"
  | "changeSpellCheckLocale"
  | "dbExport"
+ | "dbExportMailAttachmentsNotification"
  | "dbFullTextSearch"
  | "dbGetAccountDataView"
  | "dbGetAccountMail"
@@ -57,6 +58,7 @@ interface TestContext {
  | "resolveSavedProtonClientSession"
  | "saveProtonSession"
  | "selectAccount"
+ | "selectPath"
  | "spellCheck"
  | "staticInit"
  | "toggleBrowserWindow"