Add publish docs

docs/.vitepress/config.ts

@@ -37,6 +37,7 @@ export default withMermaid(
                         },
                         { text: 'Site meter', link: '/configuration/meter' },
                         { text: 'Limiters', link: '/configuration/limiters' },
+                        { text: 'Publish', link: '/configuration/publish' },
                     ],
                 },
                 {

docs/configuration/publish.md

@@ -0,0 +1,98 @@
+# Publish
+
+Optionally configure the active limits to be published to an external system.
+
+[[toc]]
+
+## MQTT
+
+Write active limits to a MQTT topic.
+
+To configure a MQTT output, add the following property to `config.json`
+
+```js
+{
+    "publish": {
+        "mqtt": {
+            "host": "mqtt://192.168.1.2", // (string) required: the MQTT broker host
+            "username": "user", // (string) optional: the MQTT broker username
+            "password": "password", // (string) optional: the MQTT broker password
+            "topic": "limits" // (string) required: the MQTT topic to write
+        }
+    }
+    ...
+}
+```
+
+The MQTT topic will contain a JSON message that meets the following schema
+
+```ts
+type ActiveInverterControlLimit = {
+    opModEnergize:
+        | {
+              value: boolean;
+              source: InverterControlTypes;
+          }
+        | undefined;
+    opModConnect:
+        | {
+              value: boolean;
+              source: InverterControlTypes;
+          }
+        | undefined;
+    opModGenLimW:
+        | {
+              value: number;
+              source: InverterControlTypes;
+          }
+        | undefined;
+    opModExpLimW:
+        | {
+              value: number;
+              source: InverterControlTypes;
+          }
+        | undefined;
+    opModImpLimW:
+        | {
+              value: number;
+              source: InverterControlTypes;
+          }
+        | undefined;
+    opModLoadLimW:
+        | {
+              value: number;
+              source: InverterControlTypes;
+          }
+        | undefined;
+};
+
+type InverterControlTypes =
+    | 'fixed'
+    | 'mqtt'
+    | 'sep2'
+    | 'twoWayTariff'
+    | 'negativeFeedIn';
+```
+
+For example
+
+```js
+{
+    "opModEnergize": {
+        "source": "sep2",
+        "value": true
+    },
+    "opModConnect": {
+        "source": "sep2",
+        "value": true
+    },
+    "opModExpLimW": {
+        "source": "sep2",
+        "value": 1500
+    },
+    "opModImpLimW": {
+        "source": "sep2",
+        "value": 1500
+    }
+}
+```