Update ProcessChallengeContext/ProcessSignOutContext.Nonce's documentation to emphasize that nonces should be generated using a crypto-secure RNG

src/OpenIddict.Client/OpenIddictClientEvents.cs

@@ -792,6 +792,8 @@ public static partial class OpenIddictClientEvents
 
         /// <summary>
         /// Gets or sets the nonce that will be used for the challenge demand, if applicable.
+        /// Note: this value MUST NOT be user-defined or extracted from any request and MUST be random
+        /// (generated by a random number generator suitable for cryptographic operations).
         /// </summary>
         public string? Nonce { get; set; }
 
@@ -931,6 +933,8 @@ public static partial class OpenIddictClientEvents
 
         /// <summary>
         /// Gets or sets the nonce that will be used for the sign-out demand, if applicable.
+        /// Note: this value MUST NOT be user-defined or extracted from any request and MUST be random
+        /// (generated by a random number generator suitable for cryptographic operations).
         /// </summary>
         public string? Nonce { get; set; }
 

src/OpenIddict.Server/OpenIddictServerHandlers.Protection.cs

@@ -1339,7 +1339,7 @@ public static partial class OpenIddictServerHandlers
                     do
                     {
                         // Note: unlike other reference tokens, user codes are meant to be used by humans,
-                        // who may have to enter it in a web form. To ensure it remains easy enough to type
+                        // who may have to enter it in a web form. To ensure they remain easy enough to type
                         // even by users with non-Latin keyboards, user codes generated by OpenIddict are
                         // only compound of 12 digits, generated using a crypto-secure random number generator.
                         // In this case, the resulting user code is estimated to have at most ~40 bits of entropy.