docs: add configuration instructions (#90)

Author: averikitsch

README.md

@@ -47,8 +47,32 @@ gemini extensions install https://github.com/gemini-cli-extensions/cloud-sql-pos
 
 ### Configuration
 
-Set the following environment variables before starting the Gemini CLI. These variables can be loaded from a `.env` file.
-This configuration is not required if utilizing the [Admin toolset](#supported-tools).
+You will be prompted to configure the following settings during installation. These settings are saved in an `.env` file within the extension's directory.
+
+*   `CLOUD_SQL_POSTGRES_PROJECT`: The GCP project ID.
+*   `CLOUD_SQL_POSTGRES_REGION`: The region of your Cloud SQL instance.
+*   `CLOUD_SQL_POSTGRES_INSTANCE`: The ID of your Cloud SQL instance.
+*   `CLOUD_SQL_POSTGRES_DATABASE`: The name of the database to connect to.
+*   `CLOUD_SQL_POSTGRES_USER`: (Optional) The database username. Defaults to the active IAM user.
+*   `CLOUD_SQL_POSTGRES_PASSWORD`: (Optional) The password for the database user.
+*   `CLOUD_SQL_POSTGRES_IP_TYPE`: (Optional) Type of the IP address: `PUBLIC`, `PRIVATE`, or `PSC`. Defaults to `PUBLIC`.
+
+> [!NOTE]
+> This configuration is primarily for the Data Plane tools (querying). The Admin toolset does not strictly require these to be pre-set if you provide them in your prompts, but it is recommended for a smoother experience.
+
+To view or update your configuration:
+
+**List Settings:**
+*   Terminal: `gemini extensions list`
+*   Gemini CLI: `/extensions list`
+
+**Update Settings:**
+*   Terminal: `gemini extensions config cloud-sql-postgresql [setting name] [--scope <scope>]`
+    *   `setting name`: (Optional) The single setting to configure.
+    *   `scope`: (Optional) The scope of the setting in (`user` or `workspace`). Defaults to `user`.
+*   Currently, you must restart the Gemini CLI for changes to take effect. We recommend using `gemini --resume` to resume your session.
+
+Alternatively, you can manually set these environment variables before starting the Gemini CLI:
 
 ```bash
 export CLOUD_SQL_POSTGRES_PROJECT="<your-gcp-project-id>"
@@ -60,10 +84,10 @@ export CLOUD_SQL_POSTGRES_PASSWORD="<your-database-password>"  # Optional
 export CLOUD_SQL_POSTGRES_IP_TYPE="PUBLIC" # Optional: `PUBLIC`, `PRIVATE`, `PSC`. Defaults to `PUBLIC`.
 ```
 
-Ensure [Application Default Credentials](https://cloud.google.com/docs/authentication/gcloud) are available in your environment.
-
 > [!NOTE]
-> If your Cloud SQL for PostgreSQL instance uses private IPs, you must run Gemini CLI in the same Virtual Private Cloud (VPC) network.
+> * Ensure [Application Default Credentials](https://cloud.google.com/docs/authentication/gcloud) are available in your environment.
+> * If your Cloud SQL for PostgreSQL instance uses private IPs, you must run Gemini CLI in the same Virtual Private Cloud (VPC) network.
+> * See [Troubleshooting](#troubleshooting) for debugging your configuration. 
 
 ### Start Gemini CLI