add generate_db_auth_token

[kyleaa]

Addresses #2

I'm not sure there's a good way to unit test this, short of just verifying the token starts with the hostname. The actual signing is tested in ex_aws.

@benwilson512 I'm not sure how the releases work in the split-repo world. This depends on the commit that was just merged into ex_aws, so as long as ex_aws_rds doesn't get a release until after that is released, it should be good to go.

[benwilson512]

@kyleaa yeah so for the release process what I'd like to do is push a patch release for ExAws itself, and then set you up with hex ownership so that you can push this package to hex.

[kyleaa]

It looks like this repo might not have a maintainer based on #1 - I'm happy to volunteer if that's the case.

[benwilson512]

Added you. ExAws 2.0.2 is out. If you send me your email address somehow I can add you as a hex maintainer