Add initial resume_at date support to HaystackBuilder

[viicslen]

Added a new method pausedUntil() that allows setting an initial resume_at date when building a Haystack. This can be used to set a longer initial delay if you are using Amazon SQS (which has a max delay of 15 minutes)

use Sammyjo20\LaravelHaystack\Models\Haystack;

// ...

Haystack::build()
        ->addJob(new NameJob('Sam'))
        ->pausedUntil(now()->addDays(5))
        ->dispatch();