Fix Kotlin default values for strings and arrays

[sigand]

To close #9844

This PR fixes two of the three issues mentioned in the linked issue. Enum default values were not a priority, as there is a reasonable workaround. All changes were tested with a minimal spec included below.

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[sigand]

{
  "openapi": "3.0.1",
  "info": {
    "title": "Test file",
    "version": "1"
  },
  "paths": { },
  "components":{
    "schemas": {
      "Test": {
        "title": "TestObject",
        "type": "object",
        "required": [
          "testArray", "stringDefault"
        ],
        "properties": {
          "stringDefault": {
            "type": "string",
            "default": "test"
          },
          "testArray": {
            "type": "array",
            "default": [],
            "items": {
              "type": "string"
            }
          },
          "testArrayOptional": {
            "type": "array",
            "default": ["1"],
            "items": {
              "type": "string"
            }
          },
          "testArrayInt": {
            "type": "array",
            "default": [1, 2],
            "uniqueItems": true,
            "items": {
              "type": "integer"
            }
          }
      }
    }
  }
}

[4brunu]

Does this PR overlap with #9849?

[sigand]

Does this PR overlap with #9849?

Yeah, somewhat.
Same solution for the String quotation problem. Though it is in different templates.
For the unique items, this one is concerned with default values, while the other seems to be concerned with the data type itself.

[wing328]

Thanks for the PR but your commit (as shown in the Commits tab) is not linked to your Github account, which means this PR won't count as your contribution in https://github.com/OpenAPITools/openapi-generator/graphs/contributors.

Let me know if you need help fixing it.

Ref: https://github.com/OpenAPITools/openapi-generator/wiki/FAQ#how-can-i-update-commits-that-are-not-linked-to-my-github-account

[wing328]

Tested kotlin-spring generator with default values for string, array of string and the result is good.

[sigand]

Thanks for the PR but your commit (as shown in the Commits tab) is not linked to your Github account, which means this PR won't count as your contribution in https://github.com/OpenAPITools/openapi-generator/graphs/contributors.

Let me know if you need help fixing it.

Ref: https://github.com/OpenAPITools/openapi-generator/wiki/FAQ#how-can-i-update-commits-that-are-not-linked-to-my-github-account

honestly, I don't care :)