Fix key length error message in ArgumentOutOfRangeException

Updated the error message in `ArgumentOutOfRangeException` to
correctly reflect the required key lengths for the algorithm.
The message now specifies that the key length must be 256, 384,
or 512 bits (32, 48, or 64 symbols), aligning with the logic
in the `switch` statement. This improves clarity and prevents
developer confusion.

Update key length logic to use UTF-8 byte count

Refactor key length validation to use UTF-8 byte count instead of symbol count. Introduced `utf8KeyLength` to calculate the byte length of the key. Updated `algorithm` selection logic to use `utf8KeyLength` for determining the appropriate `SecurityAlgorithms` value. Adjusted exception message to reflect the change, specifying key length in bytes rather than symbols.

Author: bvdcode

Sources/EasyExtensions.AspNetCore.Authorization/Extensions/ConfigurationExtensions.cs

@@ -23,12 +23,13 @@ internal static JwtSettings GetJwtSettings(this IConfiguration configuration)
             string key = (!jwtSettings.Exists() ? configuration["JwtKey"] : jwtSettings["Key"])
                 ?? throw new KeyNotFoundException("JwtSettings.Key or JwtKey is not set");
 
-            string algorithm = key.Length switch
+            int utf8KeyLength = System.Text.Encoding.UTF8.GetByteCount(key);
+            string algorithm = utf8KeyLength switch
             {
                 256 / 8 => SecurityAlgorithms.HmacSha256,
                 384 / 8 => SecurityAlgorithms.HmacSha384,
                 512 / 8 => SecurityAlgorithms.HmacSha512,
-                _ => throw new ArgumentOutOfRangeException(nameof(configuration), "Key length must be 128, 192 or 256 bits (16, 24 or 32 symbols), but was " + key.Length + " symbols.")
+                _ => throw new ArgumentOutOfRangeException(nameof(configuration), "Key length must be 256, 384 or 512 bits (32, 48 or 64 bytes), but was " + utf8KeyLength + " bytes.")
             };
 
             return new JwtSettings