[BUG] [Kotlin-spring] Multiple errors in model default values

[sigand]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

When generating models with default values, I have come across multiple bugs.
Arrays: default value is not respected
Strings: Is generated with " instead of " (double quote), which makes it not compile
Enums: Inline enums are generated with the wrong names, which makes it not compile. Note this one has a relatively easy workaround, define enums as separate schemas.

openapi-generator version

openapigenerator: 5.1.1
kotlin: 1.5.10
gradle: 7.1

OpenAPI declaration file content or url

Minimal schema

      "Test": {
        "title": "TestObject",
        "type": "object",
        "required": [  "testArray"  ],
        "properties": {
          "stringDefault": {
            "type": "string",
            "default": "test"
          },
          "testArray": {
            "type": "array",
            "default": [],
            "items": {
              "type": "string"
            }
          },
          "testArrayOptional": {
            "type": "array",
            "default": [],
            "items": {
              "type": "string"
            }
          },
          "testEnum": {
            "type": "string",
            "enum": [  "A", "B", "C"  ],
            "default": "C"
          }
        }
      }

Results

data class Test(

    @field:JsonProperty("stringDefault", required = true) val stringDefault: kotlin.String = "test",

    @field:JsonProperty("testArray", required = true) val testArray: kotlin.collections.List<kotlin.String>,

    @field:JsonProperty("testArrayOptional") val testArrayOptional: kotlin.collections.List<kotlin.String>? = null,

    @field:JsonProperty("testEnum") val testEnum: Test.TestEnum? = TestEnumEnum.c
) {

    enum class TestEnum(val value: kotlin.String) { a("A"),  b("B"), c("C") }
}

Generation Details

Using gradle

task generateExample(type: org.openapitools.generator.gradle.plugin.tasks.GenerateTask) {
    inputSpec = "$rootDir/test.json"
    generatorName = "kotlin-spring"
    outputDir = "$buildDir/generated/testing"
}

Related issues/PRs

Might be related to #8373