Simplify UInt64 Max value detection using direct enum comparison

Changed from numeric value comparison `(ulong)value == 18446744073709551615` to direct enum comparison `value == EnumU64.Max`. This is more reliable and clearer since both the symbolic EnumU64.Max and the numeric literal (EnumU64)18446744073709551615 are equivalent and will match this condition.

The fix ensures both test cases with UInt64.MaxValue (symbolic and numeric forms) are properly adjusted for MariaDB's different serialization format at runtime.

Applied to both nullable and non-nullable test methods.

Co-authored-by: renemadsen <[email protected]>

Author: Copilot

test/EFCore.MySql.FunctionalTests/Query/JsonTypesRelationalMySqlTest.cs

@@ -66,8 +66,8 @@ public override Task Can_read_write_collection_of_ulong_enum_JSON_values()
         {
             // MariaDB serializes UInt64.MaxValue as "18446744073709551615" instead of "-1"
             // Adjust the expected JSON value for MariaDB to match its actual behavior
-            // Check for both EnumU64.Max and the numeric literal (both represent UInt64.MaxValue)
-            if (AppConfig.ServerVersion.Type == ServerType.MariaDb && (ulong)value == 18446744073709551615)
+            // Check if the value is UInt64.MaxValue (works for both enum and numeric literal)
+            if (AppConfig.ServerVersion.Type == ServerType.MariaDb && value == EnumU64.Max)
             {
                 json = """{"Prop":18446744073709551615}""";
             }
@@ -88,9 +88,9 @@ public override Task Can_read_write_collection_of_ulong_enum_JSON_values()
         public async Task Can_read_write_nullable_ulong_enum_JSON_values(EnumU64? value, string json)
         {
             // MariaDB serializes UInt64.MaxValue as "18446744073709551615" instead of "-1"
-            // Adjust the expected JSON value for MariaDB to match its actual behavior
-            // Check for both EnumU64.Max and the numeric literal (both represent UInt64.MaxValue)
-            if (AppConfig.ServerVersion.Type == ServerType.MariaDb && value.HasValue && (ulong)value.Value == 18446744073709551615)
+            // Adjust the expected JSON value for MariaDB to match its actual behavior  
+            // Check if the value is UInt64.MaxValue (works for both enum and numeric literal)
+            if (AppConfig.ServerVersion.Type == ServerType.MariaDb && value.HasValue && value.Value == EnumU64.Max)
             {
                 json = """{"Prop":18446744073709551615}""";
             }