feat: add support for nullable relations

[Livijn]

Summary

This PR adds support for detecting and handling nullable relationships in model:typer.

Problem

Previously, model:typer could not detect when a relationship method had a nullable return type. For example:

public function listing(): BelongsTo|Listing|null
{
    return $this->belongsTo(Listing::class)->withTrashed();
}

This would generate listing: Listing instead of listing: Listing | null.

Solution

• Modified ModelInspector to detect nullable return types from relationship methods
• Added isReturnTypeNullable() method that checks for:
  • Union types containing null (e.g., BelongsTo|Listing|null)
  • Nullable named types (e.g., ?BelongsTo)
• Updated WriteRelationship to generate Type | null for nullable relations
• Added comprehensive tests for the new functionality

Example

Input (PHP):

public function listing(): BelongsTo|Listing|null
public function breeder(): BelongsTo|Breeder|null
public function seller(): BelongsTo|User

Output (TypeScript):

listing: Listing | null  // Nullable
breeder: Breeder | null   // Nullable
seller: User              // Required

Changes

• src/Overrides/ModelInspector.php: Override getRelations() to detect nullable return types
• src/Actions/WriteRelationship.php: Handle nullable relations with | null syntax
• test/Tests/Feature/Actions/WriteRelationshipTest.php: Add tests for nullable relations

Tests

All 116 tests passing, including 4 new tests for nullable relations.

[tcampbPPU]

hi @Livijn thanks for the PR!
Could you add a test for this for example in your comment on how it should be generated?

Output (TypeScript):

listing: Listing | null  // Nullable
breeder: Breeder | null   // Nullable
seller: User              // Required

i'd just like to reassure any changes in the future still adhere to this new functionality

Thanks again for your contributions 🍻