Display a badge for messages decrypted using shared keys (#6023)

The EXA side of element-hq/element-meta#2877: if the keys for a message have been forwarded by another user, indicate that in the UI via the text shown when tapping the event shield.

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/timeline/item/event/EventTimelineItem.kt

@@ -34,6 +34,13 @@ data class EventTimelineItem(
     val timelineItemDebugInfoProvider: TimelineItemDebugInfoProvider,
     val messageShieldProvider: MessageShieldProvider,
     val sendHandleProvider: SendHandleProvider,
+    /**
+     * If the keys to this message were forwarded by another user via history sharing (MSC4268), the ID of that user.
+     * If this is set, then [messageShieldProvider] will also return [MessageShield.AuthenticityNotGuaranteed].
+     */
+    val forwarder: UserId?,
+    /** If [forwarder] is set, the profile of the forwarding user, if it was cached at the time this `EventTimelineItem` was created. */
+    val forwarderProfile: ProfileDetails?,
 ) {
     fun inReplyTo(): InReplyTo? {
         return (content as? MessageContent)?.inReplyTo

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/timeline/item/event/EventTimelineItemMapper.kt

@@ -59,7 +59,9 @@ class EventTimelineItemMapper(
             origin = origin?.map(),
             timelineItemDebugInfoProvider = { lazyProvider.debugInfo().map() },
             messageShieldProvider = { strict -> lazyProvider.getShields(strict).map() },
-            sendHandleProvider = { lazyProvider.getSendHandle()?.let(::RustSendHandle) }
+            sendHandleProvider = { lazyProvider.getSendHandle()?.let(::RustSendHandle) },
+            forwarder = forwarder?.let { UserId(it) },
+            forwarderProfile = forwarderProfile?.map(),
         )
     }
 }

libraries/matrix/test/src/main/kotlin/io/element/android/libraries/matrix/test/timeline/TimelineFixture.kt

@@ -77,6 +77,8 @@ fun anEventTimelineItem(
     timelineItemDebugInfoProvider = debugInfoProvider,
     messageShieldProvider = messageShieldProvider,
     sendHandleProvider = sendHandleProvider,
+    forwarder = null,
+    forwarderProfile = null,
 )
 
 fun aProfileDetails(