feat: mqtt (#4841)

core/model/src/commonMain/kotlin/org/meshtastic/core/model/MqttJsonPayload.kt

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2026 Meshtastic LLC
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+package org.meshtastic.core.model
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+@Serializable
+data class MqttJsonPayload(
+    val type: String,
+    val from: Long,
+    val to: Long? = null,
+    val channel: Int? = null,
+    val payload: String? = null,
+    @SerialName("hop_limit") val hopLimit: Int? = null,
+    val id: Long? = null,
+    val time: Long? = null,
+    val sender: String? = null,
+    // Add other fields as needed for position/telemetry
+)