Examples containing date-time strings are not quoted in YAML output

[frangipanes]

Describe the bug
When I create a io.swagger.v3.oas.annotations.media.Content example with a date-time property, such as

Content(
    mediaType = MediaType.APPLICATION_JSON,
    examples = [ExampleObject(value = """{"refreshAt": "2022-03-03T12:12:16Z"}""")],
    schema = Schema(implementation = KeyUpdateCommandsResponse::class),
)

the plugin generates the following yaml output:

content:
  application/json:
    example:
      refreshAt: 2022-03-03T12:12:16Z

note that the refreshAt property is not escaped with quotation marks.

When I copy the generated yaml into the Swagger Editor, the example is rendered as:

"refreshAt": OrderedMap {}

which is incorrect.

The generated json format has the correct behaviour (but then again, it puts everything in double quotes, so to be expected).

To Reproduce
See above.

Expected behavior
the plugin generates the following yaml:

content:
  application/json:
    example:
      refreshAt: "2022-03-03T12:12:16Z"