Make Database.logger mutable

[rausnitz]

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

Database.logger is get-only, but I'd like to modify the Logger metadata and the log handler. My use-case is to track when Database.transaction is called, so I can warn when the original Database is being used before the transaction closure has been run. This is a common footgun in Vapor:

_ = try await req.db.transaction { transactionDB in
    // run a query using transactionDB
    // run a query using req.db
    // run a query using transactionDB
}

Describe the solution you'd like

Make it settable. Application.logger is settable. Request.logger is too. So it seems viable to do this.

Additional context

If the maintainers are interested in this change, I can submit a PR.

[gwynne]

Because Database has to be implemented by each individual driver, this is more complicated than it first appears - all four drivers would have to be updated individually with Concurrency-safe setters for their respective loggers, as would various baroque types such as LoggingOverrideDatabase (which, ironically, doesn't work properly anyway). This will be solved in Fluent 5, but I'm not really of a mind to deal with it for Fluent 4 at this point. That being said, if you're up for making the five different PRs (one for each driver plus one for fluent-kit) that would be needed, I'm not dead-set against it.