OpenAPI 3: Use array of objects for requestBody example

The way I would approach this would be to create a workingDay object, and pass an array of those objects in the request body. To do this, you'll want workingDay to be defined as a schema with the desired properties in the schema section under components. Notice the use of '$ref' to point an example workingDay object:

https://swagger.io/docs/specification/using-ref/

workingDay:
  description: describe my working days
  type: object
  example:
    $ref: "#/components/examples/workingDay"
  properties:
    dayIndex: 
      description: index my day
      type: foo
    dayStart: 
      description: start my day
      type: bar
    dayEnd: 
      description: end my day
      type: baz

The example object might look something like this:

https://swagger.io/docs/specification/adding-examples/

workingDay:
  summary: example values of a workingDay object
  value:
    dayIndex: 0
    dayStart: 8:00
    dayEnd: 20:00

Then when you go to describe the endpoint requestBody, it'll look more like this:

https://swagger.io/docs/specification/describing-request-body/

requestBody: 
  content:
    application/json:
      schema:
        type: object
        properties:
          name: 
            type: string
          validFrom: 
            type: string
          validTo: 
            type: string
          useHolidays: 
            type: bool
          workingDays:
            type: array
            items:
              $ref: "#/components/schemas/workingDay"