Add error handling guide

docs/.vuepress/config.js

@@ -126,6 +126,7 @@ module.exports = {
           children: [
             '/3.0.0-beta.x/guides/databases',
             '/3.0.0-beta.x/guides/deployment',
+            '/3.0.0-beta.x/guides/error-handling',
             '/3.0.0-beta.x/guides/webhooks',
           ],
         },

docs/3.0.0-beta.x/guides/error-handling.md

@@ -0,0 +1,89 @@
+# Error handling
+
+In this guide we will see how you can handle errors to send it on the Application Monitoring / Error Tracking Software you want.
+
+::: note
+In this example we will use [Sentry](https://sentry.io).
+:::
+
+## Create a middleware
+
+To handle errors, we will have to use a [middleware](../concepts/middlewares.md) that will catch errors and send them to Sentry.
+
+- Create a `./middlewares/sentry/index.js` file.
+
+**Path —** `./middlewares/sentry/index.js`
+
+```js
+module.exports = strapi => {
+  return {
+    initialize() {
+      strapi.app.use(async (ctx, next) => {
+        await next();
+      });
+    },
+  };
+};
+```
+
+## Handle errors
+
+Here is the [Node.js client documentation](https://docs.sentry.io/clients/node/)
+
+- Now add the logic that will catch errors.
+
+**Path —** `./middlewares/sentry/index.js`
+
+```js
+var Raven = require('raven');
+Raven.config('https://<key>@sentry.io/<project>').install();
+
+module.exports = strapi => {
+  return {
+    initialize() {
+      strapi.app.use(async (ctx, next) => {
+        try {
+          await next();
+        } catch (error) {
+          Raven.captureException(error);
+          throw error;
+        }
+      });
+    },
+  };
+};
+```
+
+::: warning
+It's important to `throw(error);` to not stop the middleware stack. If you don't do that, **Boom** will not structure errors messages.
+:::
+
+## Configure the middleware
+
+You will have to order this middleware at the end of the middleware stack.
+
+**Path —** `./config/middleware.json`
+
+```json
+{
+  ...
+    "after": [
+      "parser",
+      "router",
+      "sentry"
+    ]
+  }
+}
+```
+
+And fianlly you have to enable the middleware.
+
+**Path —** `./config/environments/**/middleware.json`
+
+```json
+{
+  "sentry": {
+    "enabled": true
+  }
+}
+```