Document beam-migrate tool

[ProofOfKeags]

I would love to be able to help with this as right now I am fighting through trying to figure out how to use the beam-migrate tool and package. I understand not all features are yet implemented but I had the following questions and would like to figure out how to PR some documentation in as I can get them solved.

I can currently articulate the following questions?

1. What is the MODULE component of the command that it is expecting during a beam-migrate database add _?
2. What is a valid format for the connection string? We could go with either an example or a standard if there is one.
3. Is there a way to write the DDL ourselves in Haskell, if so, is there any example code or usage that would indicate how this would work?

[ProofOfKeags]

Also what is your preferred process for docs PR's?

[mightybyte]

This would be really helpful for me as well. I'm using beam and haven't yet been able to figure out how to use the migration system.