Use JsonDict for blog post headers.

briar-headless/src/main/java/org/briarproject/briar/headless/blogs/OutputBlogPost.kt

 package org.briarproject.briar.headless.blogs
 
+import org.briarproject.bramble.api.sync.MessageId
 import org.briarproject.bramble.identity.output
 import org.briarproject.briar.api.blog.BlogPostHeader
 import org.briarproject.briar.api.blog.MessageType
+import org.briarproject.briar.headless.json.JsonDict
 
-internal fun BlogPostHeader.output(body: String) = mapOf(
-    "body" to body,
-    "author" to author.output(),
-    "authorStatus" to authorStatus.output(),
-    "type" to type.output(),
-    "id" to id.bytes,
-    "parentId" to parentId?.bytes,
-    "read" to isRead,
-    "rssFeed" to isRssFeed,
-    "timestamp" to timestamp,
-    "timestampReceived" to timeReceived
-)
+internal fun BlogPostHeader.output(body: String): JsonDict {
+    val dict = JsonDict(
+        "body" to body,
+        "author" to author.output(),
+        "authorStatus" to authorStatus.output(),
+        "type" to type.output(),
+        "id" to id.bytes,
+        "read" to isRead,
+        "rssFeed" to isRssFeed,
+        "timestamp" to timestamp,
+        "timestampReceived" to timeReceived
+    )
+    if (parentId != null) dict.put("parentId", (parentId as MessageId).bytes)
+    return dict
+}
 
 internal fun MessageType.output() = name.toLowerCase()