feat: starting member left admin handling functionality

app/src/main/java/org/thoughtcrime/securesms/database/Storage.kt

@@ -1616,6 +1616,25 @@ open class Storage(
         keys.free()
     }
 
+    override fun handleMemberLeft(message: GroupUpdated, closedGroupId: SessionId) {
+        val userGroups = configFactory.userGroups ?: return
+        val closedGroup = userGroups.getClosedGroup(closedGroupId.hexString()) ?: return
+        if (closedGroup.hasAdminKey()) {
+            // re-key and do a new config removing the previous member
+            val info = configFactory.getGroupInfoConfig(closedGroupId) ?: return
+            val members = configFactory.getGroupMemberConfig(closedGroupId) ?: return
+            val keys = configFactory.getGroupKeysConfig(closedGroupId, info, members, free = false) ?: return
+            members.erase(message.sender!!)
+
+            keys.rekey(info, members)
+
+            val
+
+        }
+
+        insertGroupInfoChange(message, closedGroupId)
+    }
+
     override fun leaveGroup(groupSessionId: String) {
         val closedGroupId = SessionId.from(groupSessionId)
         val message = GroupUpdated(

libsession/src/main/java/org/session/libsession/database/StorageProtocol.kt

@@ -172,6 +172,7 @@ interface StorageProtocol {
     fun promoteMember(groupSessionId: String, promotions: Array<String>)
     fun removeMember(groupSessionId: String, removedMembers: Array<String>, fromDelete: Boolean = false)
     fun handlePromoted(keyPair: KeyPair)
+    fun handleMemberLeft(message: GroupUpdated, closedGroupId: SessionId)
     fun leaveGroup(groupSessionId: String)
 
     // Groups

libsession/src/main/java/org/session/libsession/messaging/sending_receiving/ReceivedMessageHandler.kt

@@ -557,7 +557,7 @@ private fun handleMemberChange(message: GroupUpdated, closedGroup: SessionId) {
 
 private fun handleMemberLeft(message: GroupUpdated, closedGroup: SessionId) {
     val storage = MessagingModuleConfiguration.shared.storage
-    storage.insertGroupInfoChange(message, closedGroup)
+    storage.handleMemberLeft(message, closedGroup)
 }
 
 private fun handleGroupInfoChange(message: GroupUpdated, closedGroup: SessionId) {