It would be possible that there is no cancellable yet when unlock() is
called, then a new future is executed and it wouldn't have any
information that it is not supposed to run at all.
To solve this remember if unlock() was called and reset this in
unlock_stop().
Also implement actual unlocking in s3hlssink.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/1602>
Allow specifying an endpoint to be used for S3 requests. This makes
it possible to use integrations providing object storage based on S3
API like MinIO.
When the endpoint-uri property is specified, the endpoint resolver to
use will be overridden when making S3 requests.
STS provide temporary credentials to access AWS resource. Temporary
credentials include, AccessKeyId, SecretAccessKey and SessionToken.
With session-token property, element will be able to use temporary
credentials. When session-token is not set, element can use long
term credentials.