docs: Add docs for specifying env vars for google client secret and firebase service account key (#298)

Author: exaby73

docs/06-concepts/07-configuration.md

@@ -89,13 +89,16 @@ The following secrets are used by official Serverpod packages:
 
 - [serverpod_cloud_storage_gcp](https://pub.dev/packages/serverpod_cloud_storage_gcp): Google Cloud Storage
 - [serverpod_cloud_storage_s3](https://pub.dev/packages/serverpod_cloud_storage_s3): Amazon S3
-
-| Environment variable         | Passwords file  | Default | Description                                                               |
-| ---------------------------- | --------------- | ------- | ------------------------------------------------------------------------- |
-| SERVERPOD_HMAC_ACCESS_KEY_ID | HMACAccessKeyId | -       | The access key ID for HMAC authentication for serverpod_cloud_storage_gcp |
-| SERVERPOD_HMAC_SECRET_KEY    | HMACSecretKey   | -       | The secret key for HMAC authentication for serverpod_cloud_storage_gcp    |
-| SERVERPOD_AWS_ACCESS_KEY_ID  | AWSAccessKeyId  | -       | The access key ID for AWS authentication for serverpod_cloud_storage_s3   |
-| SERVERPOD_AWS_SECRET_KEY     | AWSSecretKey    | -       | The secret key for AWS authentication for serverpod_cloud_storage_s3      |
+- [serverpod_auth_server](https://pub.dev/packages/serverpod_auth_server): Serverpod Auth Server
+
+| Environment variable                                        | Passwords file                           | Default | Description                                                                   |
+| ----------------------------------------------------------- | ---------------------------------------- | ------- | ----------------------------------------------------------------------------- |
+| SERVERPOD_HMAC_ACCESS_KEY_ID                                | HMACAccessKeyId                          | -       | The access key ID for HMAC authentication for serverpod_cloud_storage_gcp     |
+| SERVERPOD_HMAC_SECRET_KEY                                   | HMACSecretKey                            | -       | The secret key for HMAC authentication for serverpod_cloud_storage_gcp        |
+| SERVERPOD_AWS_ACCESS_KEY_ID                                 | AWSAccessKeyId                           | -       | The access key ID for AWS authentication for serverpod_cloud_storage_s3       |
+| SERVERPOD_AWS_SECRET_KEY                                    | AWSSecretKey                             | -       | The secret key for AWS authentication for serverpod_cloud_storage_s3          |
+| SERVERPOD_PASSWORD_serverpod_auth_googleClientSecret        | serverpod_auth_googleClientSecret        | -       | The client secret for Google authentication for serverpod_auth_server         |
+| SERVERPOD_PASSWORD_serverpod_auth_firebaseServiceAccountKey | serverpod_auth_firebaseServiceAccountKey | -       | The service account key for Firebase authentication for serverpod_auth_server |
 
 #### Custom Secrets
 

docs/06-concepts/11-authentication/04-providers/02-google.md

@@ -40,6 +40,8 @@ Create the server credentials in the google cloud console. Navigate to _Credenti
 
 Download the JSON file for your web application OAuth client. This file contains both the client id and the client secret. Rename the file to `google_client_secret.json` and place it in your server's `config` directory.
 
+Alternatively, you can provide the contents of the JSON file through the environment variable `SERVERPOD_PASSWORD_serverpod_auth_googleClientSecret`.
+
 :::warning
 
 The `google_client_secret.json` contains a private key and should not be version controlled.

docs/06-concepts/11-authentication/04-providers/05-firebase.md

@@ -16,6 +16,8 @@ The server needs the service account credentials for access to your Firebase pro
 
 This will download the JSON file, rename it to `firebase_service_account_key.json` and place it in the `config` folder in your server project. Note that if this file is corrupt or if the name does not follow the convention here the authentication with firebase will fail.
 
+Alternatively, you can provide the contents of the JSON file through the environment variable `SERVERPOD_PASSWORD_serverpod_auth_firebaseServiceAccountKey`.
+
 :::danger
 The firebase_service_account_key.json file gives admin access to your Firebase project, never store it in version control.
 :::
@@ -87,8 +89,8 @@ You can also trigger the Firebase auth UI by calling the method `signInWithFireb
 
 ```dart
 await signInWithFirebase(
-  context: context, 
-  caller: client.modules.auth, 
+  context: context,
+  caller: client.modules.auth,
   authProviders: [
     firebase.PhoneAuthProvider(),
   ],