Add support for composite keys (#1479)

* Add support for composite keys

* chore: add composite foreign key test

tests/Console/ModelsCommand/Relations/Models/CompositeBelongsToVariation.php

@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Barryvdh\LaravelIdeHelper\Tests\Console\ModelsCommand\Relations\Models;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+class CompositeBelongsToVariation extends Model
+{
+    public $table = 'belongs_to_variations';
+
+    public function bothNonNullableWithForeignKeyConstraint(): BelongsTo
+    {
+        // Note, duplicating the keys here for simplicity.
+        return $this->belongsTo(
+            self::class,
+            ['not_null_column_with_foreign_key_constraint', 'not_null_column_with_foreign_key_constraint'],
+            ['not_null_column_with_foreign_key_constraint', 'not_null_column_with_foreign_key_constraint'],
+        );
+    }
+
+    public function nonNullableMixedWithoutForeignKeyConstraint(): BelongsTo
+    {
+        return $this->belongsTo(
+            self::class,
+            ['not_null_column_with_foreign_key_constraint', 'not_null_column_with_no_foreign_key_constraint'],
+            ['not_null_column_with_foreign_key_constraint', 'not_null_column_with_no_foreign_key_constraint'],
+        );
+    }
+
+    public function nullableMixedWithForeignKeyConstraint(): BelongsTo
+    {
+        return $this->belongsTo(
+            self::class,
+            ['nullable_column_with_no_foreign_key_constraint', 'not_null_column_with_foreign_key_constraint'],
+            ['nullable_column_with_no_foreign_key_constraint', 'not_null_column_with_foreign_key_constraint'],
+        );
+    }
+}