BeforeConnect Hook

[justcompile]

As per discussions in https://github.com/go-pg/pg/discussions/1848

This PR adds a new hook into Options to facilitate the use of secret providers / dynamic / one-time passwords. It has been added as BeforeConnect in order for the usage to be generic; whether it is for secret providers or simply logging when database connections are established.

Example

some error handling removed for readability

package main

imports (
    "context"
    "github.com/go-pg/pg/v10"

    "github.com/fake-user/supersecrets"
)

func main() {
    opts, _ := pg.ParseURL("postgresql://dbUser@dbhost/accounts")
   
    opts.BeforeConnect = func(ctx context.Context, o *pg.Options) error {
        token, err := supersecrets.GetToken("accounts-db-password")
        if err != nil {
            return err
        }

        o.Password = token

        return nil
    }

    db := pg.Connect(opts)

    // business logic
}

[justcompile]

Thanks for the feedback, I'll work the suggestions into this PR over the coming days

[elliotcourant]

@vmihailenco any way I'd be able to take this over? Still very interested in it

[vmihailenco]

@elliotcourant sure, go ahead :+1:

[justcompile]

@vmihailenco sorry for the horrendous delay in this. Before I get around to resolve the testing points from @elliotcourant, could I confirm whether the current changes align with your expectations around cloning Options?

[elliotcourant]

@justcompile I will take a look at the diff again this weekend and double check it!