[BUG][C#] Shouldn't replace tab, cr, lf in string enum values

Created by: kevinoid

Bug Report Checklist

Have you provided a full/minimal spec to reproduce the issue?
Have you validated the input using an OpenAPI validator (example)?
What's the version of OpenAPI Generator used?
Have you search for related issues/PRs?
What's the actual output vs expected output?
[Optional] Bounty to sponsor the fix (example)

Description

The EnumMember.Value generated for csharp (and csharp-netcore) replaces \t, \r, and \n characters with space characters. This causes values sent from the server to fail to deserialize and values sent to the server to not match the specified values.

openapi-generator version

Tested with 4.2.2 and current master (2d24d42e).

OpenAPI declaration file content or url

Example OpenAPI document

{
  "swagger": "2.0",
  "info": {
    "title": "Problematic enum strings example",
    "version": "1.0.0"
  },
  "definitions": {
    "ErrorMessage": {
      "type": "string",
      "enum": [
        "RangeError:\tToo many items.",
        "TypeError:\tInvalid type.\nCan't count multiple types.",
        "TypeError:\tInvalid type.\r\nCan't count multiple types."
      ]
    }
  },
  "paths": {
    "/count": {
      "get": {
        "operationId": "getCount",
        "responses": {
          "200": {
            "description": "Success",
            "schema": {
              "type": "integer"
            }
          },
          "default": {
            "description": "Error",
            "schema": {
              "$ref": "#/definitions/ErrorMessage"
            }
          }
        }
      }
    }
  }
}

Command line used for generation

openapi-generator generate -g csharp -i openapi.json -o generated

Steps to reproduce

Copy example OpenAPI document into openapi.json.
Run above command.
Observe that EnumMember.Value in generated/openapi/src/Org.OpenAPITools/Model/ErrorMessage.cs does not match enum in openapi.json.

Related issues/PRs

None that I could find.

Suggest a fix

DefaultCodegen.escapeText could skip removal of \t\r\n or DefaultCodegen.toEnumValue could use a different method for escaping.

Thanks for considering, Kevin