[Feature] Documentation for nginx authentication with the CLI

doc/user-guide/password.md

@@ -21,6 +21,72 @@ To enable it, simply turn the option on and set a user and a password:
 Your password isn't visible after deployment so write it down!
 ```
 
+## Basic Password Protection with the CLI
+
+Ploomber Cloud allows you to add authentication for specific features of your application using the CLI. This provides an additional layer of security for sensitive parts of your project.
+
+### Example Usage
+
+```bash
+# Add authentication for the main application
+ploomber-cloud auth --add --feature main_app
+```
+
+### Adding Authentication
+
+To add authentication for a specific feature, use the following command:
+
+```bash
+ploomber-cloud auth --add --feature <feature_name>
+```
+
+Where `<feature_name>` is one of the supported features compatible with authentication.
+
+If you don't specify a feature, you will be prompted to select one from the available options.
+
+### Options
+
+- `--overwrite`: Use this flag to overwrite existing authentication fields if they already exist.
+
+### Removing Authentication
+
+To remove authentication for a specific feature, use:
+
+```bash
+ploomber-cloud auth --remove --feature <feature_name>
+```
+
+### Important Notes
+
+1. You can only add or remove authentication at a time, not both simultaneously.
+2. At least one action (add or remove) must be specified.
+3. The `--overwrite` flag can only be used when adding authentication, not when removing.
+
+### Authentication Process
+
+When adding authentication:
+
+1. You will be prompted to enter a username and password for the selected feature.
+2. If credentials already exist in the `.env` file and `--overwrite` is not used, those credentials will be reused.
+3. The credentials are stored in the `.env` file in your project directory.
+4. The authentication configuration is added to the Ploomber Cloud configuration file (`ploomber-cloud.json`).
+
+### Credential Storage
+
+- Credentials are stored in the `.env` file in your project directory.
+- The Ploomber Cloud configuration file is updated with the authentication settings.
+
+### Warnings and Messages
+
+- If existing credentials are reused from the `.env` file, you will receive a warning message.
+- After successful authentication configuration, you will see a confirmation message and instructions for the next steps.
+
+### Permissions
+
+The `auth` command requires the user's tier to have the "authentication" permission to execute.
+You will need to upgrade if necessary.
+
+
 (auth0-integration)=
 ## Auth0 authentication
 
@@ -133,7 +199,6 @@ To log out a user, you can create a link to the `/logout` endpoint.
 
 Here's an example using **Panel**:
 
-
 ```python
 import panel as pn
 
@@ -174,7 +239,6 @@ You can set the following variables in your `.env` file to customize behavior:
 :class-container: text-center
 :gutter: 2
 
-
 :::{grid-item-card} Panel
 :link: https://github.com/ploomber/doc/tree/main/examples/panel/app-with-auth0
 :::