Support for AWS_ENDPOINT_URL_STS

[pawalt]

Describe the feature

We'd like to provide AWS_ENDPOINT_URL_STS in order to point aws-c-auth at a local STS provider. Currently, this library only supports sts.amazonaws.com.

Use Case

We'd like to use mountpoint-s3 for to mount buckets using OIDC authentication. This works fine against production AWS, but we want to use a MinIO server in development so we can write automated tests. For this, we need a custom STS URL so mountpoint-s3 can dial into MinIO instead of AWS.

Proposed Solution

Allow the default STS URL to be set:

aws-c-auth/source/credentials_provider_sts.c

Line 866 in b965ffe

impl->endpoint = aws_string_new_from_c_str(allocator, "sts.amazonaws.com");

Other Information

Crosslinking awslabs/mountpoint-s3#1203

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change