Adds bearer token authentication for the Bedrock Converse API, enabling
users to authenticate with an API key instead of SigV4/IAM credentials.
When a bearer token is available (via `options.bearerToken` or the
`AWS_BEARER_TOKEN_BEDROCK` env var), the provider:
1. Sets dummy credentials to prevent SDK credential resolution errors
2. Injects middleware after SigV4 signing that replaces the Authorization
header with `Bearer <token>` and removes SigV4-specific headers
This uses the official `bedrock:CallWithBearerToken` IAM action, which
is a documented AWS feature for API key auth on Bedrock endpoints.
Use case: users who receive a Bedrock API key (bearer token) from the
AWS console or their admin, without having IAM access keys or instance
roles. Similar to how ANTHROPIC_API_KEY works for direct Anthropic API.
Required IAM permission on the token's identity:
bedrock:CallWithBearerToken
Tested: Bearer token successfully authenticates against Bedrock Converse
API (returns correct 403 for missing IAM permission, not auth format error).
SigV4 path is unchanged when no bearer token is set.
wirjo
22085a9a17