[BUG] Nullable but required field in Go

[condorcet]

Describe the bug.

Previously nullable types were supported in scope of this issue #1418

But for now if field is required but nullable, it will not use the reference as expected.

For example if we have such schema

    schemaWithNullable:
      type: object
      required:
        - nullable_number
      properties:
        nullable_number:
          type:
            - number
            - "null"

The result will be this

type EventWithNullable struct {
  NullableNumber float64 `json:"nullable_number"` // should be *float64
}

Looks like in this condition must be used OR instead of AND (as the Java generator does)

  if (constrainedModel.options.isNullable || !required) {
    return typeWhenNullableOrOptional;
  }

Expected behavior

For nullable but required field in schema, the result should be generated with reference type, instead of value.

Screenshots

How to Reproduce

1. Grab schema with nullable and required type above.
2. Generate Go code.
3. Check appropriate field in generated Go code.

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👀 Have you checked for similar open issues?

• I checked and didn't find similar issue

🏢 Have you read the Contributing Guidelines?

• I have read the Contributing Guidelines

Are you willing to work on this issue ?

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