Scope users listing and search to current company (#607)

Add scopeWhereCompany() to User model using whereHas through the
user_company pivot table. Apply it in UsersController::index() and
SearchController so users only see members of their current company.

Previously, the users page showed ALL users across all companies.

Ref #574

app/Models/User.php

@@ -213,6 +213,13 @@ class User extends Authenticatable implements HasMedia
         return $query->where('email', 'LIKE', '%'.$email.'%');
     }
 
+    public function scopeWhereCompany($query)
+    {
+        return $query->whereHas('companies', function ($q) {
+            $q->where('company_id', request()->header('company'));
+        });
+    }
+
     public function scopePaginateData($query, $limit)
     {
         if ($limit == 'all') {