Creating new 'belongs-to' relation in Laravel with form requests - laravel

Question

I am new to Laravel and can't quite wrap my head around the Form Requests and how to use them. In simple cases, it's simple enough but what I need is a conditional creation of a related model before progressing with the rest of the request. Let me explain.
//Job model
job_id PK
client_id
some_field
//Client model
client_id
external_id
name
Now in my Create Job interface, I have a Select2 combo box that uses AJAX to search 2 different sources and can produce 3 different results.
So, say I am creating new Job and can have a POST looking like any of these:
Script found a Client with id 21, we just want to save, it all is simple
'client_id' => 21
'some_filed' => Whatever
OR
Script didn't find a Client but we did a search of external API and returned this Identifier, which I can then parse to create a new Client. This needs to be done before I save Job as I need to have a client_id ready for it
'client_id' => '196c3c7e34cde1d4593391ddf1901fd7'
'some_filed' => Whatever
OR
Script finds neither local Client nor a remote datapoint so we want to create a new Client using just the name provided. Of course this has to happen before saving the Job
'client_id' => 'My new client name'
'some_filed' => Whatever
Where do I perform all this functionality?
My first procedural guess would be to stick $data['client_id'] = Client::HandleClientAndReturnId($data['client_id']) in StoreJob's validationData() before returning the result.
But how would I handle/report possible validation issues with creating new Client and how to manage transaction - I don't want to create a Client if validation of Job fails.
I am using Form Requests and actually am parsing several models in the request already, but those are HAS_ONE type of relationships so I create them after the Job. Here I need to reverse the process. Here is what I have in my controller, if that is of any use:
class JobController extends Controller
{
public function store(StoreJob $request, StoreJobDataAdd $request_2, StoreJobDataSup $request_3)
{
$job = Job::create($request->validated());
if ($_POST['add_on']) {
$job->dataAdd()->create($request_2->validated());
}
if ($_POST['sup_on']) {
$job->dataSup()->create($request_3->validated());
}
return new JsonResponse([
'success' => true,
'message' => __('New Job has been created.')
]);
}
}
Here are my relations:
class Job extends Model
{
public function dataAdd()
{
return $this->hasOne(JobDataAdd::class, 'job_id', 'job_id');
}
public function dataSup()
{
return $this->hasOne(JobDataSup::class, 'job_id', 'job_id');
}
public function client()
{
return $this->belongsTo(Client::class, 'contact_id', 'contact_id_client');
}
}
I have a feeling I am missing the right way to do it but not quite sure where to look for the answers so please point me in the right direction.
Clarification:
The objective of the whole exercise is to allow users to create new Clients or select existing by using one combobox. It's a Select2 box. For unfamiliar - a dropdown replacement that has an ability to free-type a string that is used to search for existing records and if not found it sends to the server what user typed in. Something like a dynamic dropdown with ability to search and add options by the user.