[feature] Allow running DB migration scripts and exit

[ctron]

Is your feature request related to a problem? Please describe.

Running guac (a network process with a remote API) against a database instance with DB admin permissions feels like very bad idea.

Describe the solution you'd like

I would want to run guac migrate providing DB admin credentials. Which should run the necessary DB migrations and exit.

Describe alternatives you've considered

Provide a SQL file which one can execute.

[pxp928]

100%, during the development phase we have not secured the database connections. But going forward, we do want to use proper permissions.