Feature/protocol handlers

* Added account selection for protocol links when multiple connected accounts are available, including mailto: links
* Added support for handling mailto: links in an already-open PWA/session instead of always opening a new tab
* Added webcal: protocol handling for calendar links
* Added account selection for webcal: links when multiple calendar-capable accounts are connected
* Added an import-or-subscribe choice for detected webcal calendars
* Added protocol handler settings for registering mail and calendar handlers and choosing the open mode
* Added service worker/session coordination for passing protocol requests between browser/PWA contexts
* Added tests and translations for the new protocol handler flows

locales/en/common.json

@@ -134,6 +134,40 @@
     "nav_label": "Navigation",
     "add_app": "Apps"
   },
+  "protocol_handlers": {
+    "title": "Default apps",
+    "description": "Choose whether email and calendar links open in Bulwark. Technically, Bulwark registers as a protocol handler for mailto: and webcal: links.",
+    "unsupported": "This browser or connection does not support manual protocol-handler registration. You may still be able to use the installed PWA via browser or OS settings.",
+    "mailto_label": "Email links",
+    "mailto_description": "Open mailto: links in Bulwark with a prefilled composer.",
+    "protocol_open_mode_label": "When opening protocol links",
+    "protocol_open_mode_description": "Choose whether Bulwark opens mailto: and webcal: links in a new tab or reuses an open session. The active-session option needs notification permission so you can click a fallback notification to bring Bulwark to the front if the browser blocks focus.",
+    "protocol_open_mode_active_session": "Open in active session if possible",
+    "protocol_open_mode_new_tab": "Always open a new tab",
+    "focus_notification_title": "Open Bulwark",
+    "focus_notification_body": "The link was opened in Bulwark. Click to bring the window to the front.",
+    "webcal_label": "Calendar links",
+    "webcal_description": "Open webcal: links in Bulwark with a prefilled calendar subscription dialog.",
+    "register_mailto": "Register email app",
+    "register_webcal": "Register calendar app",
+    "mailto_registered": "Email handler registration requested",
+    "webcal_registered": "Calendar handler registration requested",
+    "registration_failed": "Protocol handler registration failed",
+    "opening_mailto": "Opening composer...",
+    "opening_webcal": "Opening calendar...",
+    "browser_note": "Your browser or operating system may ask you to confirm this and may require Bulwark to be installed before it can be selected as the default app.",
+    "select_account_title": "Choose account",
+    "select_mailto_account": "Choose which account should open this email link.",
+    "select_webcal_account": "Choose which account should open this calendar link.",
+    "select_account_note": "This only applies to this protocol link.",
+    "detail_to": "To",
+    "detail_subject": "Subject",
+    "detail_no_subject": "No subject",
+    "detail_calendar": "Calendar",
+    "detail_source": "Source",
+    "active_account": "Active",
+    "switching_account": "Switching account..."
+  },
   "sidebar_apps": {
     "modal_title": "Sidebar Apps",
     "add_new": "Add App",
@@ -736,6 +770,7 @@
       "files": "Files",
       "contacts": "Contacts",
       "encryption": "Encryption",
+      "protocol_handlers": "Default apps",
       "sidebar_apps": "Sidebar Apps",
       "notifications": "Notifications",
       "layout": "Layout",
@@ -2445,6 +2480,15 @@
       "file_too_large": "File exceeds 10MB limit",
       "invalid_format": "Invalid calendar file format"
     },
+    "webcal_action": {
+      "title": "Open calendar link",
+      "description": "How would you like to use \"{name}\"?",
+      "import_title": "Import once",
+      "import_description": "Fetch the events now and copy them into one of your calendars.",
+      "subscribe_title": "Subscribe",
+      "subscribe_description": "Keep this calendar synced automatically as a separate calendar.",
+      "cancel": "Cancel"
+    },
     "management": {
       "title": "Calendar Management",
       "description": "Create, rename, and customize your calendars. Right-click a calendar in the sidebar to quickly change its color.",