perf(model-client): stricter limit of the body size in pushObjects

The body was previously limit by the number of entries, but some entries are bigger than others.
In some cases the body was too big causing a `413 Request Entity Too Large`.
Now that actual serialized size of the entries is used to split them into chunks.

Author: slisson

model-client/src/commonMain/kotlin/org/modelix/model/client2/ModelClientV2.kt

@@ -322,22 +322,33 @@ class ModelClientV2(
 
     override suspend fun pushObjects(repository: RepositoryId, objects: Sequence<ObjectHashAndSerializedObject>) {
         LOG.debug { "${clientId.toString(16)}.pushObjects($repository)" }
-        objects.chunked(100_000).forEach { unsortedChunk ->
-            // Entries are sorted to avoid deadlocks on the server side between transactions.
-            // Since ignite locks individual entries, this is equivalent to a lock ordering.
-            // This is also fixed on the server side, but there might an old version of the server running that doesn't
-            // contain this fix. This client-side sorting could be removed in a future version when all servers
-            // are upgraded.
-            val chunk = unsortedChunk.sortedBy { it.first }
+        val maxBodySize = 16 * 1024 * 1024
+        val chunkContent = StringBuilder(1024 * 1024)
+
+        suspend fun sendChunk() {
             httpClient.put {
                 url {
                     takeFrom(baseUrl)
                     appendPathSegmentsEncodingSlash("repositories", repository.id, "objects")
                 }
                 contentType(ContentType.Text.Plain)
-                setBody(chunk.flatMap { it.toList() }.joinToString("\n"))
+                setBody(chunkContent.toString())
+            }
+            chunkContent.clear()
+        }
+
+        val itr = objects.iterator()
+        while (itr.hasNext()) {
+            val entry = itr.next()
+            val entrySize = (if (chunkContent.isEmpty()) 0 else 1) + entry.first.length + 1 + entry.second.length
+            if (chunkContent.length + entrySize > maxBodySize) {
+                sendChunk()
+            } else {
+                if (chunkContent.isNotEmpty()) chunkContent.append('\n')
+                chunkContent.append(entry.first).append('\n').append(entry.second)
             }
         }
+        if (chunkContent.isNotEmpty()) sendChunk()
     }
 
     override suspend fun pull(branch: BranchReference, lastKnownVersion: IVersion?): IVersion {