feat: support configuration through environment variables

Author: reevejd

README.md

@@ -21,10 +21,28 @@ jupyter serverextension enable --py jupyterlab_s3_browser
 
 to make sure the serverextension is enabled and then restart (stop and start) JupyterLab.
 
+## Usage
+
+#### Configuration
+
+If you have a ~/.aws/credentials file available or have already set up role-based access then no futher configuration is necessary.
+
+If you wish to configure through environment variables, you can do so using environment variables, for example:
+
+bash```
+export JUPYTERLAB_S3_ENDPOINT="https://s3.us.cloud-object-storage.appdomain.cloud"
+export JUPYTERLAB_S3_ACCESS_KEY_ID="my-access-key-id"
+export JUPYTERLAB_S3_SECRET_ACCESS_KEY="secret"
+
+```
+
+You can also start without any configuration and fill in your endpoint/credentials though the form when prompted.
+
 #### Amazon SageMaker
 
 [View installation instructions specific to SageMaker here.](docs/SAGEMAKER.md) Thanks to [Bipin Pandey](https://github.com/Bipin007) for helping figure this out.
 
 ## Contributing
 
 Contributions to this extension are welcome! [View CONTRIBUTING.md to get started.](docs/CONTRIBUTING.md)
+```

jupyterlab_s3_browser/__init__.py

@@ -6,6 +6,7 @@
 import logging
 import traceback
 from collections import namedtuple
+from os import environ
 
 import boto3
 import tornado.gen as gen
@@ -24,9 +25,21 @@ class S3Config(SingletonConfigurable):
     Allows configuration of access to an S3 api
     """
 
-    endpoint_url = Unicode("", config=True, help="The url for the S3 api")
-    client_id = Unicode("", config=True, help="The client ID for the S3 api")
-    client_secret = Unicode("", config=True, help="The client secret for the S3 api")
+    endpoint_url = Unicode(
+        environ.get("JUPYTERLAB_S3_ENDPOINT", ""),
+        config=True,
+        help="The url for the S3 api",
+    )
+    client_id = Unicode(
+        environ.get("JUPYTERLAB_S3_ACCESS_KEY_ID", ""),
+        config=True,
+        help="The client ID for the S3 api",
+    )
+    client_secret = Unicode(
+        environ.get("JUPYTERLAB_S3_SECRET_ACCESS_KEY", ""),
+        config=True,
+        help="The client secret for the S3 api",
+    )
 
 
 @singleton