Introduce --use-iso-date-format CLI tool argument

[christianhelle]

This resolves #66 which was reported by @brease-colin

This introduces the --use-iso-date-format CLI tool argument that explicitly formats date query string parameters in ISO 8601 standard date format using delimiters (yyyy-MM-dd <-> 2023-06-15)

USAGE:
    refitter [URL or input file] [OPTIONS]

EXAMPLES:
    refitter ./openapi.json
    refitter https://petstore3.swagger.io/api/v3/openapi.yaml
    refitter ./openapi.json --namespace "Your.Namespace.Of.Choice.GeneratedCode" --output ./GeneratedCode.cs
    refitter ./openapi.json --namespace "Your.Namespace.Of.Choice.GeneratedCode" --internal
    refitter ./openapi.json --output ./IGeneratedCode.cs --interface-only
    refitter ./openapi.json --use-api-response
    refitter ./openapi.json --cancellation-tokens
    refitter ./openapi.json --no-operation-headers
    refitter ./openapi.json --use-iso-date-format

ARGUMENTS:
    [URL or input file]    URL or file path to OpenAPI Specification file

OPTIONS:
                                      DEFAULT                                                                           
    -h, --help                                         Prints help information                                          
    -n, --namespace                   GeneratedCode    Default namespace to use for generated types                     
    -o, --output                      Output.cs        Path to Output file                                              
        --no-auto-generated-header                     Don't add <auto-generated> header to output file                 
        --interface-only                               Don't generate contract types                                    
        --use-api-response                             Return Task<IApiResponse<T>> instead of Task<T>                  
        --internal                                     Set the accessibility of the generated types to 'internal'       
        --cancellation-tokens                          Use cancellation tokens                                          
        --no-operation-headers                         Don't generate operation headers                                 
        --no-logging                                   Don't log errors or collect telemetry                            
        --use-iso-date-format                          Explicitly format date query string parameters in ISO 8601       
                                                       standard date format using delimiters (2023-06-15)               

The following example OpenAPI spec:

{
  "swagger": "2.0",
  "info": {
    "title": "XX",
    "version": "0.0.0"
  },
  "host": "x.io",
  "basePath": "/",
  "schemes": [
    "https"
  ],
  "paths": {
    "/t/dummy/{employee_id}": {
      "get": {
        "summary": "X",
        "description": "X",
        "operationId": "dummy",
        "parameters": [
          {
            "name": "employee_id",
            "in": "path",
            "description": "the specific employee",
            "required": true,
            "format": "int64",
            "type": "integer"
          },
          {
            "name": "valid_from",
            "in": "query",
            "description": "the start of the period",
            "required": true,
            "format": "date",
            "type": "string"
          },
          {
            "name": "valid_to",
            "in": "query",
            "description": "the end of the period",
            "required": true,
            "format": "date",
            "type": "string"
          }
        ],
        "responses": {
          "200": {
            "description": "No response was specified",
            "schema": {
              "$ref": "#/definitions/DummyList"
            }
          }
        },
        "produces": [
          "application/json",
          "application/xml"
        ]
      }
    },
  }
}

generates the following code when using the --use-iso-date-format CLI tool argument

public interface IXX
{
    /// <summary>
    /// X
    /// </summary>
    [Get("/t/dummy/{employee_id}")]
    Task Dummy(long employee_id, [Query(Format = "yyyy-MM-dd")] System.DateTimeOffset valid_from, [Query(Format = "yyyy-MM-dd")] System.DateTimeOffset valid_to);
}