Please explain the motivation behind the feature request:

Amazon Bedrock announced in July 2025 support for API Keys as auth method as an alternative to IAM credentials.

This will simplify onboarding and configuration when using the provider.

Describe the solution you'd like:

By default the AWS SDKs look for an environment variable named AWS_BEARER_TOKEN_BEDROCK, which can also be passed as a bearer token in a direct HTTP request (Authorization: Bearer $AWS_BEARER_TOKEN_BEDROCK).

We'd like to have support for this same env var in the Goose AWS Bedrock provider, in addition to the already supported AWS credentials chain.

• I have verified this does not duplicate an existing feature request