feat: add core attribute, contract, and exception classes for transformer

- Implemented `Transform` attribute in `src/Attribute/Transform.php`:
  - Extends `BaseProcessorAttribute` to mark properties for transformation processing.

- Defined `TransformationResult` interface in `src/Contract/TransformationResult.php`:
  - Provides contract methods for result validation, error handling, and transformed data retrieval.

- Created `TransformerException` in `src/Exception/TransformerException.php`:
  - Extends `AbstractException` to handle transformer-specific errors.
  - Added methods `invalidInput`, `invalidFormat`, and `invalidType` with detailed error codes and messages for input type, format, and type validation.

Author: walmir-silva

src/Attribute/Transform.php

@@ -0,0 +1,12 @@
+<?php
+
+declare(strict_types=1);
+
+namespace KaririCode\Transformer\Attribute;
+
+use KaririCode\Contract\Processor\Attribute\BaseProcessorAttribute;
+
+#[\Attribute(\Attribute::TARGET_PROPERTY)]
+final class Transform extends BaseProcessorAttribute
+{
+}

src/Contract/TransformationResult.php

@@ -0,0 +1,16 @@
+<?php
+
+declare(strict_types=1);
+
+namespace KaririCode\Transformer\Contract;
+
+interface TransformationResult
+{
+    public function isValid(): bool;
+
+    public function getErrors(): array;
+
+    public function getTransformedData(): array;
+
+    public function toArray(): array;
+}

src/Exception/TransformerException.php

@@ -0,0 +1,58 @@
+<?php
+
+declare(strict_types=1);
+
+namespace KaririCode\Transformer\Exception;
+
+use KaririCode\Exception\AbstractException;
+
+final class TransformerException extends AbstractException
+{
+    private const CODE_INVALID_INPUT = 5001;
+    private const CODE_INVALID_FORMAT = 5002;
+    private const CODE_INVALID_TYPE = 5003;
+
+    public static function invalidInput(string $expectedType, string $actualType): self
+    {
+        $message = sprintf(
+            'Invalid input type. Expected %s, got %s.',
+            $expectedType,
+            $actualType
+        );
+
+        return self::createException(
+            self::CODE_INVALID_INPUT,
+            'INVALID_INPUT_TYPE',
+            $message
+        );
+    }
+
+    public static function invalidFormat(string $format, string $value): self
+    {
+        $message = sprintf(
+            'Invalid format. Expected format %s, got %s.',
+            $format,
+            $value
+        );
+
+        return self::createException(
+            self::CODE_INVALID_FORMAT,
+            'INVALID_FORMAT',
+            $message
+        );
+    }
+
+    public static function invalidType(string $expectedType): self
+    {
+        $message = sprintf(
+            'Invalid type. Expected %s.',
+            $expectedType
+        );
+
+        return self::createException(
+            self::CODE_INVALID_TYPE,
+            'INVALID_TYPE',
+            $message
+        );
+    }
+}