Feature: @toJson / @toYaml operators for config generation

[lukacsi]

Problem

Generating ConfigMaps and Secrets with structured content requires building files as @concat strings with manually escaped quotes and \n:

stringData:
  config.yaml:
    "@concat":
      - "server_name: \""
      - "$.Source.spec.name"
      - "\"\n"
      - "database:\n"
      - "  host: \""
      - "$.Source.spec.dbHost"
      - "\"\n"

This is error-prone, unreadable, and unmaintainable. Any operator managing applications needs config generation, and @concat doesn't scale for it.

Proposal

@toJson and @toYaml operators that serialize a structured object (with embedded expressions) to a string:

stringData:
  config.yaml:
    "@toYaml":
      server_name: "$.Source.spec.name"
      database:
        host: "$.Source.spec.dbHost"
        port: "$.Source.spec.dbPort"

• Recursively evaluate expressions, then serialize
• Nested operators (@concat, @cond, @definedOr) work inside
• Output is a string for ConfigMap/Secret values