Add http and https proxy feature

Added new proxy feature based on http and https proxy agents.
Proxy feature works like notifications, there is many proxy
could be related one proxy entry.

Supported features
- Proxies can activate and disable in bulk
- Proxies auto enabled by default for new monitors
- Proxies could be applied in bulk to current monitors
- Both authenticated and anonymous proxies supported
- Export and import support for proxies

server/proxy.js

@@ -0,0 +1,99 @@
+const { R } = require("redbean-node");
+
+class Proxy {
+
+    /**
+     * Saves and updates given proxy entity
+     *
+     * @param proxy
+     * @param proxyID
+     * @param userID
+     * @return {Promise<Bean>}
+     */
+    static async save(proxy, proxyID, userID) {
+        let bean;
+
+        if (proxyID) {
+            bean = await R.findOne("proxy", " id = ? AND user_id = ? ", [proxyID, userID]);
+
+            if (!bean) {
+                throw new Error("proxy not found");
+            }
+
+        } else {
+            bean = R.dispense("proxy");
+        }
+
+        // Make sure given proxy protocol is supported
+        if (!["http", "https"].includes(proxy.protocol)) {
+            throw new Error(`Unsupported proxy protocol "${proxy.protocol}. Supported protocols are http and https."`);
+        }
+
+        // When proxy is default update deactivate old default proxy
+        if (proxy.default) {
+            await R.exec("UPDATE proxy SET `default` = 0 WHERE `default` = 1");
+        }
+
+        bean.user_id = userID;
+        bean.protocol = proxy.protocol;
+        bean.host = proxy.host;
+        bean.port = proxy.port;
+        bean.auth = proxy.auth;
+        bean.username = proxy.username;
+        bean.password = proxy.password;
+        bean.active = proxy.active || true;
+        bean.default = proxy.default || false;
+
+        await R.store(bean);
+
+        if (proxy.applyExisting) {
+            await applyProxyEveryMonitor(bean.id, userID);
+        }
+
+        return bean;
+    }
+
+    /**
+     * Deletes proxy with given id and removes it from monitors
+     *
+     * @param proxyID
+     * @param userID
+     * @return {Promise<void>}
+     */
+    static async delete(proxyID, userID) {
+        const bean = await R.findOne("proxy", " id = ? AND user_id = ? ", [proxyID, userID]);
+
+        if (!bean) {
+            throw new Error("proxy not found");
+        }
+
+        // Delete removed proxy from monitors if exists
+        await R.exec("UPDATE monitor SET proxy_id = null WHERE proxy_id = ?", [proxyID]);
+
+        // Delete proxy from list
+        await R.trash(bean);
+    }
+}
+
+/**
+ * Applies given proxy id to monitors
+ *
+ * @param proxyID
+ * @param userID
+ * @return {Promise<void>}
+ */
+async function applyProxyEveryMonitor(proxyID, userID) {
+    // Find all monitors with id and proxy id
+    const monitors = await R.getAll("SELECT id, proxy_id FROM monitor WHERE user_id = ?", [userID]);
+
+    // Update proxy id not match with given proxy id
+    for (const monitor of monitors) {
+        if (monitor.proxy_id !== proxyID) {
+            await R.exec("UPDATE monitor SET proxy_id = ? WHERE id = ?", [proxyID, monitor.id]);
+        }
+    }
+}
+
+module.exports = {
+    Proxy,
+};