feat: support both ticket link directions (KAN-12)

app/Http/Controllers/Api/ProjectTicketLinkController.php

@@ -36,11 +36,12 @@ class ProjectTicketLinkController extends ApiController
 
         $ticketLink = $this->storeProjectTicketLink->handle($project, $ticket, $user, $request->validated());
         $ticketLink->setAttribute('current_ticket_id', $ticket->id);
+        $label = $ticketLink->ticketLinkType->labelForSource($ticketLink->source_ticket_id === $ticket->id);
 
         return TicketLinkResource::make($ticketLink->load(['sourceTicket', 'targetTicket', 'ticketLinkType']))
             ->additional([
                 'meta' => [
-                    'message' => "{$ticketLink->ticketLinkType->label} link was saved.",
+                    'message' => "{$label} link was saved.",
                 ],
             ])
             ->response()

app/Http/Controllers/ProjectTicketLinkController.php

@@ -34,9 +34,10 @@ class ProjectTicketLinkController extends Controller
         );
 
         $ticketLink = $this->storeProjectTicketLink->handle($project, $ticket, $user, $request->validated());
+        $label = $ticketLink->ticketLinkType->labelForSource($ticketLink->source_ticket_id === $ticket->id);
 
         return to_route('projects.tickets.show', [$project, $ticket])
-            ->with('status', "{$ticketLink->ticketLinkType->label} link was saved.");
+            ->with('status', "{$label} link was saved.");
     }
 
     public function destroy(

app/Http/Requests/StoreTicketLinkRequest.php

@@ -42,6 +42,7 @@ class StoreTicketLinkRequest extends FormRequest
                     fn ($query) => $query->where('project_id', $project->id),
                 ),
             ],
+            'link_direction' => ['sometimes', 'required', Rule::in(['source', 'counterpart'])],
         ];
     }