Switch to using tailscale oauth api

This removes the need to update the API key every 90 days.

README.md

@@ -73,7 +73,8 @@ Configuration values can be set using environment variables, or optionally loade
 - **interval** (`TAILSCALESD_INTERVAL`): The interval on which the Tailscale API is polled in seconds. Default is `60`.
 - **bearer_token** (`TAILSCALESD_BEARER_TOKEN`): The authentication token passed in the Authorization header (required).
 - **tailnet** (`TAILSCALESD_TAILNET`): The Tailscale tailnet identifier (required).
-- **api_key** (`TAILSCALESD_API_KEY`): The Tailscale API key (required).
+- **client_id** (`TAILSCALESD_CLIENT_ID`): The Tailscale oauth client id (required).
+- **client_secret** (`TAILSCALESD_CLIENT_SECRET`): The Tailscale oauth client secret (required).
 
 #### Environment File
 
@@ -83,7 +84,8 @@ You can also specify an environment file to load configuration values. The path
 
 ```env
 TAILSCALESD_TAILNET=my-tailnet
-TAILSCALESD_API_KEY=my-api-key
+TAILSCALESD_CLIENT_ID=xxxx
+TAILSCALESD_CLIENT_SECRET=yyyyy
 TAILSCALESD_HOST=127.0.0.1
 TAILSCALESD_BEARER_TOKEN=supersecret
 ```
@@ -101,6 +103,9 @@ This service provides the following Prometheus metrics:
   - **Description**: The number times a matrix sd host was unreachable. This counter increments each time a connection attempt to a matrix sd host fails.
   - **Labels**:
     - `device_hostname`: The hostname of the device that was unreachable.
+- `tailscalesd_polling_up`
+  - **Type**: Gauge
+  - **Description**: Indicates if tailscalesd can access the tailscale devices API up (1) or down (0)
 
 It also provides HTTP server metrics from [trallnag/prometheus-fastapi-instrumentator](https://github.com/trallnag/prometheus-fastapi-instrumentator)