refactor(CryptographerExtensions): Aktualisiert zur Verwendung von IUniqueSecurityContext anstelle von IRSACryptographer.

- umbenannt in SecurityExtensions.

DigitalData.Core.Abstractions/Security/SecurityExtensions.cs

@@ -0,0 +1,21 @@
+namespace DigitalData.Core.Abstractions.Security
+{
+    public static class SecurityExtensions
+    {
+        public static IEnumerable<TUniqueSecurityContext> GetByIssuer<TUniqueSecurityContext>(this IEnumerable<TUniqueSecurityContext> contextes, string issuer) where TUniqueSecurityContext: IUniqueSecurityContext
+            => contextes.Where(c => c.Issuer == issuer);
+
+        public static IEnumerable<TUniqueSecurityContext> GetByAudience<TUniqueSecurityContext>(this IEnumerable<TUniqueSecurityContext> contextes, string audience) where TUniqueSecurityContext : IUniqueSecurityContext
+            => contextes.Where(c => c.Audience == audience);
+
+        public static TUniqueSecurityContext Get<TUniqueSecurityContext>(this IEnumerable<TUniqueSecurityContext> contextes, string issuer, string audience) where TUniqueSecurityContext : IUniqueSecurityContext
+            => contextes.Where(c => c.Issuer == issuer && c.Audience == audience).SingleOrDefault()
+            ?? throw new InvalidOperationException($"Exactly one {typeof(TUniqueSecurityContext).Name} must exist with Issuer: '{issuer}' and Audience: '{audience}'.");
+
+        public static bool TryGet<TUniqueSecurityContext>(this IEnumerable<TUniqueSecurityContext> contextes, string issuer, string audience, out TUniqueSecurityContext? context) where TUniqueSecurityContext : IUniqueSecurityContext
+        {
+            context = contextes.SingleOrDefault(c => c.Issuer == issuer && c.Audience == audience);
+            return context is not null;
+        }
+    }
+}