🪨 feat: AWS default credentials chain (#123)

pages/docs/configuration/pre_configured_ai/bedrock.mdx

@@ -4,6 +4,8 @@ Head to the [AWS docs](https://docs.aws.amazon.com/bedrock/latest/userguide/gett
 
 You’ll also need to turn on model access for your account, which you can do by [following these instructions](https://docs.aws.amazon.com/bedrock/latest/userguide/model-access.html).
 
+## Authentication
+
 - You will need to set the following environment variables:
 
 ```bash filename=".env"
@@ -12,7 +14,25 @@ BEDROCK_AWS_ACCESS_KEY_ID=your_access_key_id
 BEDROCK_AWS_SECRET_ACCESS_KEY=your_secret_access_key
 ```
 
-Note: Other ways to authenticate are still in development.
+**Note:** You can also omit the access keys in order to use the default AWS credentials chain but you must set the default region:
+
+```bash filename=".env"
+BEDROCK_AWS_DEFAULT_REGION=us-east-1
+```
+
+Doing so prompts the credential provider to find credentials from the following sources (listed in order of precedence):
+
+- Environment variables exposed via process.env
+- SSO credentials from token cache
+- Web identity token credentials
+- Shared credentials and config ini files
+- The EC2/ECS Instance Metadata Service
+
+The default credential provider will invoke one provider at a time and only continue to the next if no credentials have been located.
+
+For example, if the process finds values defined via the `AWS_ACCESS_KEY_ID` and `AWS_SECRET_ACCESS_KEY` environment variables, the files at ~/.aws/credentials and ~/.aws/config will not be read, nor will any messages be sent to the Instance Metadata Service.
+
+## Configuring models
 
 - You can optionally specify which models you want to make available with `BEDROCK_AWS_MODELS`: