Support redocly's `x-enumDescriptions` OpenAPI extension

[jhassine]

Ref: https://redocly.com/docs/realm/author/reference/openapi-extensions/x-enum-descriptions#openapi-extension-x-enumdescriptions

For example:

from django.db import models
from django.utils.translation import gettext_lazy as _

class YearInSchool(models.TextChoices):
    FRESHMAN = "FR", _("Freshman")
    SOPHOMORE = "SO", _("Sophomore")
    JUNIOR = "JR", _("Junior")
    SENIOR = "SR", _("Senior")
    GRADUATE = "GR", _("Graduate")

the label values could be extracted and used as x-enumdescriptions.