✨ Support additionalProperties schema for structured map fields

[pierrecdn]

📑 Description

Add support for JSON Schema additionalProperties on object types, enabling maps with structured values (in addition to lists) to render as proper forms instead of flat key/json-value text inputs.

Backend:

• Parse additionalProperties in helm schema (using a custom RawJSON type to handle both boolean and object values from json-iterator)
• Map it to a new AdditionalProperties field on the Field model
• Propagate through the schema-to-field mapper

Frontend:

• Split MapField into FlatMapField (existing behavior) and StructuredMapField
• Update form value converters (mapsToArray / findMaps) to handle structured map entries

✅ Checks

• I have tested my code (provide screenshots or screen recordings of a working solution)
• I have performed a self-review of my code

ℹ Additional context

Correspond to the following schema:

"workers": {
      "type": "object",
      "description": "Map of worker pools, keyed by pool name.",
      "additionalProperties": {
        "type": "object",
        "required": [
          "replicaCount"
        ],
        "properties": {
          "replicaCount": {
            "type": "number",
            "description": "Number of workers to run"
          },
          "flavor": {
            "default": "u1.small",
            "enum": [
              "u1.small",
              "u1.large",
            ],
            "type": "string",
            "description": "Type of VM worker"
          },
          "os": {
            "default": "ubuntu",
            "type": "string",
            "enum": [
              "ubuntu",
              "centos",
              "windows"
            ],
            "description": "Base image of the VM"
          }
        }
      },
      "title": "workers"
    }