Add MessageService and IndividualSendJobV2.

core/serialization/src/main/java/org/signal/core/util/serialization/SignalJson.kt

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2026 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.signal.core.util.serialization
+
+import arrow.core.Either
+import arrow.core.raise.either
+import kotlinx.serialization.DeserializationStrategy
+import kotlinx.serialization.SerializationException
+import kotlinx.serialization.SerializationStrategy
+import kotlinx.serialization.json.Json
+
+/**
+ * Helper for working with JSON.
+ */
+object SignalJson {
+
+  val json = Json { ignoreUnknownKeys = true }
+
+  inline fun <reified T> encode(input: T): Either<EncodeError, String> = either {
+    try {
+      json.encodeToString(input)
+    } catch (e: SerializationException) {
+      raise(EncodeError.BadInput(e))
+    }
+  }
+
+  inline fun <reified T> encode(serializer: SerializationStrategy<T>, input: T): Either<EncodeError, String> = either {
+    try {
+      json.encodeToString(serializer, input)
+    } catch (e: SerializationException) {
+      raise(EncodeError.BadInput(e))
+    }
+  }
+
+  inline fun <reified T> decode(input: String): Either<DecodeError, T> = either {
+    try {
+      json.decodeFromString<T>(input)
+    } catch (e: SerializationException) {
+      raise(DecodeError.BadInput(e))
+    } catch (e: IllegalStateException) {
+      raise(DecodeError.BadClassAssignment(e))
+    }
+  }
+
+  fun <T> decode(deserializer: DeserializationStrategy<T>, input: String): Either<DecodeError, T> = either {
+    try {
+      json.decodeFromString(deserializer, input)
+    } catch (e: SerializationException) {
+      raise(DecodeError.BadInput(e))
+    } catch (e: IllegalStateException) {
+      raise(DecodeError.BadClassAssignment(e))
+    }
+  }
+
+  sealed class EncodeError(val cause: Exception) {
+    data class BadInput(val error: SerializationException) : EncodeError(error)
+  }
+
+  sealed class DecodeError(val cause: Exception) {
+    data class BadInput(val error: SerializationException) : DecodeError(error)
+    data class BadClassAssignment(val error: IllegalStateException) : DecodeError(error)
+  }
+}