Hardened EOSEAccountFast against concurrent access so callers no longer iterate over live mutable maps

amethyst/src/main/java/com/vitorpamplona/amethyst/service/relays/EOSE.kt

@@ -125,12 +125,14 @@ class EOSEAccountFast<T : Any>(
     cacheSize: Int = 20,
 ) {
     private val users: LruCache<T, EOSERelayList> = LruCache<T, EOSERelayList>(cacheSize)
+    private val lock = Any()
 
     fun addOrUpdate(
         user: T,
         relayUrl: NormalizedRelayUrl,
         time: Long,
     ) {
+        synchronized(lock) {
             val relayList = users[user]
             if (relayList == null) {
                 val newList = EOSERelayList()
@@ -141,20 +143,28 @@ class EOSEAccountFast<T : Any>(
                 relayList.addOrUpdate(relayUrl, time)
             }
         }
+    }
 
     fun removeEveryoneBut(list: Set<T>) {
+        synchronized(lock) {
             users.snapshot().forEach {
                 if (it.key !in list) {
                     users.remove(it.key)
                 }
             }
         }
-
-    fun removeDataFor(user: T) {
-        users.remove(user)
     }
 
-    fun since(key: T) = users[key]?.relayList
+    fun removeDataFor(user: T) {
+        synchronized(lock) {
+            users.remove(user)
+        }
+    }
+
+    fun since(key: T): SincePerRelayMap? =
+        synchronized(lock) {
+            users[key]?.relayList?.toMutableMap()
+        }
 
     fun newEose(
         user: T,