Update the package description of OpenIddict.AspNetCore and tweak nullable references

src/OpenIddict.AspNetCore/OpenIddict.AspNetCore.csproj

@@ -7,7 +7,7 @@
   </PropertyGroup>
 
   <PropertyGroup>
-    <Description>Versatile OpenID Connect stack for ASP.NET Core 2.1, 3.1 and 5.0.</Description>
+    <Description>Versatile OpenID Connect stack for ASP.NET Core.</Description>
     <PackageTags>$(PackageTags);aspnetcore;server;validation</PackageTags>
   </PropertyGroup>
 

src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkApplicationStore.cs

@@ -1002,7 +1002,7 @@ public class OpenIddictEntityFrameworkApplicationStore<TApplication, TAuthorizat
             return default;
         }
 
-        return (TKey) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
+        return (TKey?) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
     }
 
     /// <summary>

src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkAuthorizationStore.cs

@@ -877,7 +877,7 @@ public class OpenIddictEntityFrameworkAuthorizationStore<TAuthorization, TApplic
             return default;
         }
 
-        return (TKey) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
+        return (TKey?) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
     }
 
     /// <summary>

src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkScopeStore.cs

@@ -702,7 +702,7 @@ public class OpenIddictEntityFrameworkScopeStore<TScope, TContext, TKey> : IOpen
             return default;
         }
 
-        return (TKey) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
+        return (TKey?) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
     }
 
     /// <summary>

src/OpenIddict.EntityFramework/Stores/OpenIddictEntityFrameworkTokenStore.cs

@@ -908,7 +908,7 @@ public class OpenIddictEntityFrameworkTokenStore<TToken, TApplication, TAuthoriz
             return default;
         }
 
-        return (TKey) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
+        return (TKey?) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
     }
 
     /// <summary>

src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreApplicationStore.cs

@@ -1043,7 +1043,7 @@ public class OpenIddictEntityFrameworkCoreApplicationStore<TApplication, TAuthor
             return default;
         }
 
-        return (TKey) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
+        return (TKey?) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
     }
 
     /// <summary>

src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreAuthorizationStore.cs

@@ -476,7 +476,7 @@ public class OpenIddictEntityFrameworkCoreAuthorizationStore<TAuthorization, TAp
             throw new ArgumentNullException(nameof(authorization));
         }
 
-        if (authorization.CreationDate == null)
+        if (authorization.CreationDate is null)
         {
             return new ValueTask<DateTimeOffset?>(result: null);
         }
@@ -966,7 +966,7 @@ public class OpenIddictEntityFrameworkCoreAuthorizationStore<TAuthorization, TAp
             return default;
         }
 
-        return (TKey) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
+        return (TKey?) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
     }
 
     /// <summary>

src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreScopeStore.cs

@@ -718,7 +718,7 @@ public class OpenIddictEntityFrameworkCoreScopeStore<TScope, TContext, TKey> : I
             return default;
         }
 
-        return (TKey) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
+        return (TKey?) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
     }
 
     /// <summary>

src/OpenIddict.EntityFrameworkCore/Stores/OpenIddictEntityFrameworkCoreTokenStore.cs

@@ -984,7 +984,7 @@ public class OpenIddictEntityFrameworkCoreTokenStore<TToken, TApplication, TAuth
             return default;
         }
 
-        return (TKey) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
+        return (TKey?) TypeDescriptor.GetConverter(typeof(TKey)).ConvertFromInvariantString(identifier);
     }
 
     /// <summary>