Support _comment fields in state machine JSON for documentation

[ottobot-ai]

Problem

The SDK state machines include _comment fields for documentation purposes:

{
  "states": {
    "Idle": {
      "_comment": "Initial state before market opens"
    }
  }
}

However, OttoChain's Circe decoders reject unknown fields, causing validation errors.

Options

1. Ignore unknown fields — Update Circe decoder config with .withDefaults + filter unknown keys
2. Explicit support — Add optional _comment: Option[String] to State/Transition case classes
3. Keep SDK clean — Remove all _comment fields from SDK (current workaround)

Current Status

PR #47 removed _comment fields as a workaround. This issue tracks adding proper support.

Related

• ottochain-services PR fix(ci): use explicit cache key including plugins.sbt #47
• ottochain-sdk PR feat(validation): reject reserved JSON Logic operators as field names #12