feat(auth): introduce rate limit service interface

- Define RateLimitService abstract class with checkRequest and dispose methods
- Implement rate limiting logic to prevent abuse of sensitive or expensive endpoints
- Use unique key (e.g., IP address) to track and limit requests
- Throw ForbiddenException when rate limit is exceeded
- Provide flexibility for different rate limiting strategies in implementations

Author: fulleni

lib/src/services/rate_limit_service.dart

@@ -0,0 +1,37 @@
+import 'package:core/core.dart';
+
+/// {@template rate_limit_service}
+/// Defines the interface for a service that provides rate-limiting capabilities.
+///
+/// This service is used to check and record requests against a specific key
+/// (e.g., an IP address or email) to prevent abuse of sensitive or expensive
+/// endpoints.
+/// {@endtemplate}
+abstract class RateLimitService {
+  /// {@macro rate_limit_service}
+  const RateLimitService();
+
+  /// Checks if a request associated with the given [key] is allowed.
+  ///
+  /// This method performs the following logic:
+  /// 1. Counts the number of recent requests for the [key] within the [window].
+  /// 2. If the count is greater than or equal to the [limit], it throws a
+  ///    [ForbiddenException] indicating the rate limit has been exceeded.
+  /// 3. If the count is below the limit, it records the current request
+  ///    (e.g., by storing a timestamp) and allows the request to proceed.
+  ///
+  /// - [key]: A unique identifier for the request source (e.g., IP address).
+  /// - [limit]: The maximum number of requests allowed within the window.
+  /// - [window]: The time duration to consider for counting requests.
+  ///
+  /// Throws [ForbiddenException] if the rate limit is exceeded.
+  /// Throws [OperationFailedException] for unexpected errors during the check.
+  Future<void> checkRequest({
+    required String key,
+    required int limit,
+    required Duration window,
+  });
+
+  /// Disposes of any resources used by the service (e.g., timers).
+  void dispose();
+}