Would it be possible to modify the S3 sync feature to support AWS temporary credentials? I work in an AWS environment that won't allow the creation of IAM users, but we're able to use temporary credentials via a named profile.
From the AWS documentation, it looks like the only difference to authenticate with temporary credentials is adding the token to the request.
Looking through the code, it seems like the basic functionality could be achieved by adding a new field in the setting.ts file to ingest the token, in addition to the username/password. Then in the lib/synctargetamazons3.js, adding the session token to the credentials. That way if it's blank, it relies on the previous method, but if the token is filled in, it gets passed to AWS.
It would also be neat to have Joplin be able to pull this from the ~/.aws/credentials file by specifying the name of the named profile, but that would probably take more effort.