docs: adding information about environments (#674)

* docs: adding information about environments

* fix format

* fix typos

* format

Author: erickzanardo

docs/docs/basics/enviroments.md

@@ -0,0 +1,61 @@
+---
+sidebar_position: 7
+title: 🌱 Environments
+---
+
+# Environments 🌱
+
+---
+
+The ability of configuring different environments is necessary for any real world applications.
+
+The application needs to be able be configured to run a development environment, or a staging one
+and ultimately, a production one.
+
+There are many ways that different environments can be achieved in a Dart Frog application, the
+out of the box one is by making the use of environment variables, which is a feature provided
+directly from the Dart SDK.
+
+As seen in the Dependency injection example, middleware can be used to provide dependencies
+to the application.
+
+Following that approach, the snippet bellow can be used to exemplify how a database client that
+can be is configured through different environments can be provided to the application.
+
+```dart
+Handler middleware(Handler handler) {
+  return handler
+      .use(provider<CardsRepository>((_) {
+        return DatabaseClient(
+          dbUrl: Platform.environment['DB_URL'],
+          dbUser: Platform.environment['DB_USER'],
+          dbPassword: Platform.environment['DB_PASSWORD'],
+        );
+      }),
+    );
+}
+```
+
+Then, when running the server, those variables can be passed along directly on the Dart Frog
+commands, like:
+
+For development server:
+
+```bash
+DB_URL=... DB_USER=... DB_PASSWORD=... dart_frog server
+```
+
+For production server
+
+```bash
+DB_URL=... DB_USER=... DB_PASSWORD=... dart build/server.dart
+```
+
+For convenience, these variables can also be exported in the current session.
+
+:::warning
+Commonly used in Flutter applications, accessing variables through `String.fromEnvironment` in
+a Dart frog application will not work, that method is meant to accesses variables set by the dart
+compiler or runtime, which doesn't apply on a Dart frog application. Due that
+`Platform.environment` should be used instead.
+:::

docs/docs/basics/resources.md

@@ -1,5 +1,5 @@
 ---
-sidebar_position: 7
+sidebar_position: 8
 title: 📚 Additional Resources
 ---