Add Campaigns module for grouping short links.

Let accounts organise links by promo or launch, attach or detach links, and view combined click totals from the sidebar.

app/Models/User.php

@@ -49,6 +49,11 @@ class User extends Authenticatable
         return $this->hasMany(ShortLink::class);
     }
 
+    public function campaigns(): HasMany
+    {
+        return $this->hasMany(Campaign::class);
+    }
+
     public function linkCustomDomains(): HasMany
     {
         return $this->hasMany(LinkCustomDomain::class);