don't print URL when url.Parse returns an error

[heavycrystal]

When pgx.Connector pgx.ParseConfig is used, it indirectly calls url.Parse which by default returns the URL as part of its error type in case it failed to parse it. This leads to the error message from pgx leaking the unredacted URL in any logs.

Fixed by typecasting to url.Error and then returning only the appropriate bit of the error, needed to change a variable name along with this.

Minimal Reproduction

package main

import (
    "context"
    "fmt"
    "os"

    "github.com/jackc/pgx/v5"
)

func main() {
    conn, err := pgx.Connect(context.Background(), "postgres://postgres:password@ localhost:5432/postgres")
    if err != nil {
        fmt.Fprintf(os.Stderr, "Unable to connect to database: %v\n", err)
        os.Exit(1)
    }
    defer conn.Close(context.Background())
}

Without the change

Unable to connect to database: cannot parse `postgres://postgres:xxxxxx@ localhost:5432/postgres`: failed to parse as URL (parse "postgres://postgres:password@ localhost:5432/postgres": invalid character " " in host name)

With the change

Unable to connect to database: cannot parse `postgres://postgres:xxxxxx@ localhost:5432/postgres`: failed to parse as URL (invalid character " " in host name)