improve drafts flows

tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/utils/DraftIdAllocator.kt

@@ -0,0 +1,25 @@
+package dev.inmo.tgbotapi.utils
+
+import dev.inmo.tgbotapi.types.DraftId
+import kotlinx.coroutines.NonCancellable.isActive
+import kotlinx.coroutines.sync.Mutex
+import kotlinx.coroutines.sync.withLock
+import kotlin.random.Random
+
+class DraftIdAllocator {
+    val allocated = mutableSetOf<DraftId>()
+    val mutex = Mutex()
+
+    suspend fun allocate(): DraftId = mutex.withLock {
+        while (isActive) {
+            val draftId = DraftId(Random.nextLong())
+            if (allocated.add(draftId)) {
+                return draftId
+            }
+        }
+        error("Unable to allocate a unique draft ID")
+    }
+    suspend fun free(draftId: DraftId) = mutex.withLock {
+        allocated.remove(draftId)
+    }
+}