add getPostsIds methodfor ReadPostsAPI

core/src/commonMain/kotlin/com/insanusmokrassar/postssystem/core/post/api/ReadPostsAPI.kt

@@ -13,6 +13,11 @@ import com.soywiz.klock.DateTime
  * Simple read API by different properties
  */
 interface ReadPostsAPI {
+    /**
+     * @return [Set] of [PostId]s which can be used to get data using [getPostById]
+     */
+    suspend fun getPostsIds(): Set<PostId>
+
     /**
      * @return [RegisteredPost] if it is available by [id]
      */

core/src/commonTest/kotlin/com/insanusmokrassar/postssystem/core/api/InMemoryPostsAPI.kt

@@ -63,7 +63,7 @@ class InMemoryPostsAPI(
         } != null
     }
 
-
+    override suspend fun getPostsIds(): Set<PostId> = posts.keys.toSet()
     override suspend fun getPostById(id: PostId): RegisteredPost? = posts[id]
     override suspend fun getPostsByContent(id: ContentId): List<RegisteredPost> =
         posts.values.filter { post -> id in post.content }