Add upload save feature

Add /api/upload-save endpoint that streams the data via the slave
assigned to the target instance to the instance saves directory, along
with a ctl command and web interface button to do the upload.

packages/master/src/Master.js

@@ -2,7 +2,6 @@
 const compression = require("compression");
 const events = require("events");
 const express = require("express");
-const expressFileupload = require("express-fileupload");
 const fs = require("fs-extra");
 const http = require("http");
 const https = require("https");
@@ -49,6 +48,7 @@ class Master {
 
 		this.app = express();
 		this.app.locals.master = this;
+		this.app.locals.streams = new Map();
 
 		/**
 		 * Mapping of slave id to slave info
@@ -336,7 +336,6 @@ class Master {
 			hitCounter.inc();
 			next();
 		});
-		app.use(expressFileupload());
 		app.use(compression());
 
 		// Set folder to serve static content from (the website)
@@ -492,6 +491,41 @@ class Master {
 			});
 		};
 	}
+
+	/**
+	 * Forward the given request to the slave contaning the instance
+	 *
+	 * Finds the slave which the instance with the given instance ID is
+	 * currently assigned to and forwards the request to that instance.
+	 * The request data must have an instance_id parameter.
+	 *
+	 * @param {module:lib/link.Request} request - The request to send.
+	 * @param {object} data - Data to pass with the request.
+	 * @param {number} data.instance_id -
+	 *     ID of instance to send this request towards
+	 * @returns {object} data returned from the request.
+	 */
+	async forwardRequestToInstance(request, data) {
+		let instance = this.instances.get(data.instance_id);
+		if (!instance) {
+			throw new libErrors.RequestError(`Instance with ID ${data.instance_id} does not exist`);
+		}
+
+		let slaveId = instance.config.get("instance.assigned_slave");
+		if (slaveId === null) {
+			throw new libErrors.RequestError("Instance is not assigned to a slave");
+		}
+
+		let connection = this.wsServer.slaveConnections.get(slaveId);
+		if (!connection) {
+			throw new libErrors.RequestError("Slave containing instance is not connected");
+		}
+		if (request.plugin && !connection.plugins.has(request.plugin)) {
+			throw new libErrors.RequestError(`Slave containing instance does not have ${request.plugin} plugin`);
+		}
+
+		return await request.send(connection, data);
+	}
 }
 
 module.exports = Master;