Add httpserver API docs

docs/Plugin API/httpserver.md

@@ -0,0 +1,49 @@
+<a name="httpserver"></a>
+
+## httpserver : <code>object</code>
+Add features to PostalPoint's integrated LAN HTTP API server.
+
+**Kind**: global namespace  
+
+* [httpserver](#httpserver) : <code>object</code>
+    * [.addEndpoint(id, onCall)](#httpserver.addEndpoint)
+    * [.getServerPort()](#httpserver.getServerPort) ⇒ <code>number</code>
+    * [.getClientKey()](#httpserver.getClientKey) ⇒ <code>string</code>
+
+<a name="httpserver.addEndpoint"></a>
+
+### httpserver.addEndpoint(id, onCall)
+Add a custom HTTP JSON POST endpoint to the LAN HTTP API server running inside
+PostalPoint.  Requests must be POSTed and contain a JSON body (or empty body, which will be converted to `null`).
+
+**Kind**: static method of [<code>httpserver</code>](#httpserver)  
+
+| Param | Type | Description |
+| --- | --- | --- |
+| id | <code>string</code> | Endpoint ID. Used in URL, for example: `http://<host>:7678/<id>` |
+| onCall | <code>function</code> | Async function to call when the endpoint is called, which returns the response. |
+
+**Example**  
+```js
+global.apis.httpserver.addEndpoint("testendpoint", async function (request) {
+    if (request.abc == "123") {
+        // A non-string `body` is converted to JSON before the HTTP reply is sent.
+        return {body: {json: true, abc: 123}, httpcode: 200, contentType: "application/json"};
+    }
+    // A string `body` is sent to the client as-is using whatever contentType you specify.
+    return {body: "abc", httpcode: 200, contentType: "text/plain"};
+});
+```
+<a name="httpserver.getServerPort"></a>
+
+### httpserver.getServerPort() ⇒ <code>number</code>
+Get the local HTTP server's port number.
+
+**Kind**: static method of [<code>httpserver</code>](#httpserver)  
+<a name="httpserver.getClientKey"></a>
+
+### httpserver.getClientKey() ⇒ <code>string</code>
+Get the local machine's HTTP client key it uses to authenticate with other
+installations of PostalPoint on the LAN.
+
+**Kind**: static method of [<code>httpserver</code>](#httpserver)