fix: correct format on resolve tester base64 encoded json

[nicklasl]

Previously the resulting json contained the context value type which meant that while the base64 decoding worked in the Confidence app the resolve was not working properly.

JSON Format Examples - Before vs After

Before the Fix (Incorrect - Type Wrappers)

The Confidence SDK was incorrectly serializing context with type wrapper objects:

  {
    "flag": "flags/test-flag",
    "context": {
      "visitor_id": {"string": "bcd97b13-ddad-4ee8-9331-aeac06370bd9"},
      "targeting_key": {"string": "test-user-123"},
      "user": {
        "map": {
          "country": {"string": "SE"},
          "age": {"integer": 25},
          "product": {"string": "premium"},
          "fraud-score": {"double": 0.7}
        }
      }
    },
    "clientKey": "test-client-secret"
  }

Issues:

• Values wrapped in type objects like {"string": "value"}, {"integer": 25}, {"double": 0.7}
• Nested structures wrapped in {"map": {...}}
• Not usable with the Resolve tester tool

After the Fix (Correct - Clean JSON)

The Confidence SDK now produces clean JSON matching the OpenFeature provider:

  {
    "flag": "flags/test-flag",
    "context": {
      "visitor_id": "bcd97b13-ddad-4ee8-9331-aeac06370bd9",
      "targeting_key": "test-user-123",
      "user": {
        "country": "SE",
        "age": 25,
        "product": "premium",
        "fraud-score": 0.7
      }
    },
    "clientKey": "test-client-secret"
  }

[fabriziodemaria]

Thanks for the samples in the PR description, made the review easy and smooth