feature: Approval and Promotion to VigilCareClinical

VigilCareRecordsAPI/Services/Interfaces/IIdempotencyService.cs

@@ -0,0 +1,14 @@
+public interface IIdempotencyService
+{
+    /// <summary>
+    /// Returns the cached response if the key was already used, or null if this is a new key.
+    /// </summary>
+    Task<IdempotencyRecord?> GetExistingAsync(string idempotencyKey, string operationName);
+
+    /// <summary>
+    /// Stores the result of an operation for future deduplication.
+    /// Must be called within the same transaction as the operation.
+    /// </summary>
+    Task SaveAsync(string idempotencyKey, string operationName, Guid resourceId,
+        int httpStatusCode, object responseBody, TimeSpan? ttl = null);
+}