fix(nestjs): improve type schema generation for string, enum, and array types

[hyeonss0417]

Summary

Fix incorrect OpenAPI schema generation for string, enum, and array types in NestJS parser.

Problem

The following types were being incorrectly converted to { type: 'object', additionalProperties: ... }:

1. String properties - key: string → { type: 'object', additionalProperties: { type: 'string' } }
2. Enum properties - gender: Gender → { type: 'object', additionalProperties: ... }
3. Array properties - users: UserDto[] → { type: 'object', additionalProperties: { $ref: '...' } }

Root Cause

TypeScript's getIndexInfosOfType() returns index signatures for:

• Primitive types (string[number] → string)
• Enum types (union of literals)
• Array types (T[])

These were incorrectly treated as Record<K, V> or Map<K, V> types.

Solution

Added checks in getIndexSignatureInfoFromType() to skip:

• Primitive types (string, number, boolean, etc.)
• Array types (T[] or Array<T>)
• Enum types (union of literals or TypeFlags.Enum)

Additional Changes

• TJS Integration: Added typescript-json-schema as fallback for types not found in typeDefinitions
• Async Support: Made generateOpenApiFromNest async for TJS schema conversion
• Test Coverage: Added test for array property types to prevent regression

Testing

• All 132 tests pass
• Added new test case: should handle array properties correctly (not as Record/Map)

Example

Before:

"subscriptionProducts": {
  "type": "object",
  "additionalProperties": {
    "$ref": "#/components/schemas/SubscriptionProductDto"
  }
}

After:

"subscriptionProducts": {
  "type": "array",
  "items": {
    "$ref": "#/components/schemas/SubscriptionProductDto"
  }
}

[github-actions]

LGTM 👍