Add serialization support for ValidationSettings

This commit introduces a new serialization context for the
`ValidationSettings` type in the `ApiJsonSerializerContext` class
by adding an additional `[JsonSerializable]` attribute. This change
enables the JSON serializer to handle `ValidationSettings` for
serialization and deserialization processes.

Author: Timothy Dodd

src/LogMkAgent/Common/ApiJsonSerializerContext.cs

@@ -7,6 +7,7 @@ namespace LogMkAgent;
 [JsonSerializable(typeof(List<LogLine>))]
 [JsonSerializable(typeof(IEnumerable<LatestDeploymentEntry>))]
 [JsonSerializable(typeof(IEnumerable<LogLine>))]
+[JsonSerializable(typeof(ValidationSettings))]
 public partial class ApiJsonSerializerContext : JsonSerializerContext
 {
 }