docs: document Backblaze B2 (S3-compatible) as a model repository backend

docs/user_guide/model_repository.md

@@ -167,6 +167,39 @@ export TRITON_AWS_MOUNT_DIRECTORY=/path/to/your/local/directory
 
 **Make sure, that `TRITON_AWS_MOUNT_DIRECTORY` exists on your local machine and it is empty.**
 
+##### S3-compatible object stores
+
+The S3 backend also works with any endpoint that implements the S3-compatible API, such as Backblaze B2, Cloudflare R2, and MinIO. The repository path uses the private-instance form described above, with the provider's endpoint as the host, and the credentials and region are passed through the same environment variables as Amazon S3.
+
+```bash
+$ tritonserver --model-repository=s3://https://s3.us-west-2.amazonaws.com:443/bucket/path/to/model/repository ...
+```
+
+Replace `s3.us-west-2.amazonaws.com:443` with the S3-compatible endpoint and port for your provider and region.
+
+```bash
+$ export AWS_ACCESS_KEY_ID="<access_key_id>"
+$ export AWS_SECRET_ACCESS_KEY="<secret_access_key>"
+$ export AWS_DEFAULT_REGION="us-west-2"
+$ tritonserver --model-repository=s3://https://s3.us-west-2.amazonaws.com:443/my-bucket/models ...
+```
+
+The credential file described in [Cloud Storage with Credential file (Beta)](#cloud-storage-with-credential-file-beta) can also be used for an S3-compatible endpoint by adding an `s3` entry keyed by the bucket URI, including the custom endpoint when used.
+
+```json
+{
+  "s3": {
+    "s3://https://s3.us-west-2.amazonaws.com:443/my-bucket": {
+      "secret_key": "<secret_access_key>",
+      "key_id": "<access_key_id>",
+      "region": "us-west-2",
+      "session_token": "",
+      "profile": ""
+    }
+  }
+}
+```
+
 #### Azure Storage
 
 For a model repository residing in Azure Storage, the repository path must be prefixed with as://.