Add auth support

[TheEadie]

Description

Allow users to authenticate with Flyway automatically by providing email, token, and agree-to-eula inputs. When both email and token are provided, the action runs flyway auth after installation.

Related issue

N/a

Check list

• Mark if documentation changes are required.
• Mark if tests were added or updated to cover the changes.

[DoodleBobBuffPants]

The change is fine, just some thoughts:

• There are a few ways to authenticate, such as supplying permits / offline permits. Should we be adding support for those? What about documenting which environment variables to set vs adding inputs?
• Should authenticating be a separate action, in particular for those users that would use offline permits and will have Flyway already available on self-hosted agents so they do not need to make external network calls

[TheEadie]

The change is fine, just some thoughts:

* There are a few ways to authenticate, such as supplying permits / offline permits. Should we be adding support for those? What about documenting which environment variables to set vs adding inputs?

* Should authenticating be a separate action, in particular for those users that would use offline permits and will have Flyway already available on self-hosted agents so they do not need to make external network calls

I suspect if you're using offline permits then you'll be in a non-internet connected environment and won't be able to make use of the Action. Similarly I think the seperate Action would hit the same issue. In those case we probably need better documentation on how to set up offline agents.