Allow DB commands against external databases

[ipmb]

Currently the CLI checks the settings to determine if a database is attached.

apppack/app/app.go

Lines 1102 to 1103 in d150d9f

	// DBShellTaskInfo gets the family and command to execute for a db shell task
	func (a *App) DBShellTaskInfo() (*string, *string, error) {

We should fallback to checking if a config value for DATABASE_URL is set and attempting to connect to whatever is defined there. This would allow the CLI to run DB commands against external providers like Neon, Crunchy, etc.