Restructure solution layout by module

src/Authority/StellaOps.Authority/StellaOps.Auth.Client/IStellaOpsTokenCache.cs

@@ -0,0 +1,25 @@
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace StellaOps.Auth.Client;
+
+/// <summary>
+/// Abstraction for caching StellaOps tokens.
+/// </summary>
+public interface IStellaOpsTokenCache
+{
+    /// <summary>
+    /// Retrieves a cached token entry, if present.
+    /// </summary>
+    ValueTask<StellaOpsTokenCacheEntry?> GetAsync(string key, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Stores or updates a token entry for the specified key.
+    /// </summary>
+    ValueTask SetAsync(string key, StellaOpsTokenCacheEntry entry, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Removes the cached entry for the specified key.
+    /// </summary>
+    ValueTask RemoveAsync(string key, CancellationToken cancellationToken = default);
+}