feat(deeplink): point deeplinks at HealthChat hosts

Claims app.healthchat.ch and to.healthchat.ch as App Links, registers the
healthchat:// scheme, and drops the unreachable mobile.element.io handling.

docs/deeplink.md

@@ -1,4 +1,4 @@
-# Element X Android deeplink
+# HealthChat Android deeplink
 
 <!--- TOC -->
 
@@ -12,31 +12,45 @@
 
 ## Introduction
 
-Element X Android supports deep linking to specific screens in the application. This document explains how to use deep links in Element X Android.
+HealthChat Android supports deep linking to specific screens in the application. This document explains how to use deep links in HealthChat Android.
 
 ### Asset Links
 
-The asset links file is available at https://element.io/.well-known/assetlinks.json
+Two hosts are claimed as verified Android App Links, and each one must serve a matching asset links
+file listing `ch.healthchat.element` and the SHA-256 of the Play app signing certificate:
+
+| Host | Asset links file | Served from |
+|---|---|---|
+| `app.healthchat.ch` | https://app.healthchat.ch/.well-known/assetlinks.json | the `element-web` fork (`apps/web/res/.well-known/assetlinks.json`) |
+| `to.healthchat.ch` | https://to.healthchat.ch/.well-known/assetlinks.json | the `healthchat-matrix.to` fork (generated by `scripts/build.js`) |
 
 ### Supported links
 
-Element Call link: 
-> https://call.element.io/Example
-
 Link to a user:
-> https://app.element.io/#/user/@alice:matrix.org
+> https://to.healthchat.ch/#/@alice:healthchat.ch
+> https://app.healthchat.ch/#/user/@alice:healthchat.ch
 
 Link to a room by id or alias:
-> https://app.element.io/#/room/!roomid:matrix.org
-> https://app.element.io/#/room/#element-x-android:matrix.org
+> https://to.healthchat.ch/#/!roomid:healthchat.ch
+> https://app.healthchat.ch/#/room/#healthchat:healthchat.ch
 
 Link to a room with a specific event:
-> https://app.element.io/#/room/!roomid:matrix.org/$eventid
+> https://app.healthchat.ch/#/room/!roomid:healthchat.ch/$eventid
 
-Note that it will also work with other domain such as:
-> https://mobile.element.io
-> https://develop.element.io
-> https://staging.element.io
+The HealthChat matrix.to deployment hands out a custom scheme to Android, which is registered too:
+> healthchat://room/%23healthchat%3Ahealthchat.ch
+> healthchat://user/%40alice%3Ahealthchat.ch
+
+Standard Matrix URIs also work:
+> matrix:r/healthchat:healthchat.ch
+
+Only the two hosts above are declared in the manifest, so only those open the app from a browser.
+`DefaultMatrixToConverter` is host-agnostic though: any URL using the `/#/room/`, `/#/user/` or
+`/#/group/` path, as well as plain matrix.to links, are still resolved once they reach the app
+(for instance when tapped inside a message).
+
+Finally, notifications use an internal deep link that is not browsable:
+> healthchat://open/{sessionId}/{roomId}/{eventId}
 
 ## Developer tools
 
@@ -44,28 +58,34 @@ Using an Android 12 or higher emulator
 
 Ensure links verification is enabled
 ```bash
-adb shell am compat enable 175408749 io.element.android.x.debug  
+adb shell am compat enable 175408749 ch.healthchat.element.debug  
 ```
 
 Reset link verifications for the given package id
 ```bash
-adb shell pm set-app-links --package io.element.android.x.debug 0 all 
+adb shell pm set-app-links --package ch.healthchat.element.debug 0 all 
 ```
 
 Force the package id links to be verified
 ```bash
-adb shell pm verify-app-links --re-verify io.element.android.x.debug 
+adb shell pm verify-app-links --re-verify ch.healthchat.element.debug 
 ```
 
 Print the link verification of the package id
 ```bash
-adb shell pm get-app-links io.element.android.x.debug
+adb shell pm get-app-links ch.healthchat.element.debug
 ```
 
 ```
-  io.element.android.x.debug:
+  ch.healthchat.element.debug:
     ID: e2ece472-c266-4bf0-829c-be79959a6270
     Signatures: [B0:B0:51:DC:56:5C:81:2F:E1:7F:6F:3E:94:5B:4D:79:04:71:23:AB:0D:A6:12:86:76:9E:B2:94:91:97:13:0E]
     Domain verification state:
-      *.element.io: 1024
+      app.healthchat.ch: verified
+      to.healthchat.ch: verified
 ```
+
+Verification only succeeds if the signature above is listed in the asset links files. Release builds
+are signed by Google Play, so use the app signing certificate SHA-256 from the Play Console. For a
+debug build, add the fingerprint of `app/signature/debug.keystore` (alias `androiddebugkey`) to both
+files, or test with `healthchat://` links instead, which need no verification.