Django リレーションされた2つのテーブルにINSERT処理　【CreateView】

下記　どうしても自力解決が難しく、お力添えいただけますよう、よろしくおねがいします。

【やりたいこと】

リレーションされた2つのテーブルにCreateViewにて同時に登録する

【課題点（エラーにより困っていること）】

子テーブルへINSERT処理をする際に、親テーブルで登録した主キーが取得できずにAttributeErrorが発生します。
確認内容をソースコード内でコメントとしています。

【エラーメッセージ】

AttributeError at /quotation/registration/
'RegistrationForm' object has no attribute 'quotation_id'

【form内容(下記print確認内容)】

<tr><th><label for="id_client_id">顧客:</label></th><td><select name="client_id" required id="id_client_id"> <option value="">---------</option> <option value="1" selected>顧客名</option>
</select></td></tr>
<tr><th><label for="id_username">作成者:</label></th><td><select name="username" required id="id_username"> <option value="">---------</option> <option value="1" selected>aaaa</option>
</select></td></tr>
<tr><th><label for="id_expiry">見積有効期限:</label></th><td><input type="text" name="expiry" value="ご下命後1ヶ月間" maxlength="255" id="id_expiry"></td></tr> <tr><th><label for="id_recipient">宛名:</label></th><td><input type="text" name="recipient" value="宛名" maxlength="255" id="id_recipient"></td></tr> <tr><th><label for="id_title">件名:</label></th><td><input type="text" name="title" value="件名" maxlength="255" id="id_title"></td></tr> <tr><th><label for="id_delivery_time">納期:</label></th><td><input type="text" name="delivery_time" value="納期" maxlength="255" id="id_delivery_time"></td></tr> <tr><th><label for="id_payment_term">取引条件:</label></th><td><input type="text" name="payment_term" value="取引条件" maxlength="255" id="id_payment_term"></td></tr> <tr><th><label for="id_consumption_tax">消費税額:</label></th><td><input type="number" name="consumption_tax" value="1" required id="id_consumption_tax"></td></tr> <tr><th><label for="id_remark">備考:</label></th><td><textarea name="remark" cols="40" rows="10" id="id_remark"> 備考</textarea></td></tr>

【ソースコード】

【Views.py】
import logging
from django.urls import reverse_lazy
from django.views import generic
from .forms import QuotationsForm, RegistrationForm, Quotations_details_formSet
from django.contrib import messages
from django.contrib.auth.mixins import LoginRequiredMixin
from .models import Quotations, Quotations_details
from django.db import transaction

logger = logging.getLogger(__name__)

class RegistrationView(LoginRequiredMixin, generic.CreateView):
    model = Quotations, Quotations_details
    template_name = "registration.html"
    form_class = RegistrationForm
    form_class_Quotations_details = Quotations_details_formSet
    success_url = reverse_lazy('quotation:registration')

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        Quotations_details_form = self.form_class_Quotations_details(self.request.GET or None)
        context.update({'Quotations_details_form':Quotations_details_form})
        return context

    def form_valid(self, form):
        Quotations_details_form = self.form_class_Quotations_details(self.request.POST or None) 


        if Quotations_details_form.is_valid():
            with transaction.atomic():
              form.save()　#【この親テーブルへのinsert処理までは正常に行われています。　公式ドキュメントでは、このタイミングで主キーの設定値を保存していると表記あり（https://djangoproject.jp/doc/ja/1.0/ref/models/instances.html）最新のドキュメントでも同じような実装が確認できました。（https://docs.djangoproject.com/ja/3.1/intro/tutorial02/）】
              print(form) #【RegistrationFormでfieldsとして、quotation_idが存在していますが、formの中身を確認すると存在していませんでした。】
              Quotations_details_form.insrance.quotation_id = form.quotation_id #【ここでAttributeErrorが発生します。】
              Quotations_details_form.save()
              messages.success(self.request,'登録が完了しました。')
              logger.info('Inquiry sent by{}'.format(form.cleaned_data['name']))
        else:
            self.form_invalid(form)

        return HttpResponseRedirect(self.get_success_url())


    def form_invalid(self, form):
        messages.error(self.request,'登録ができませんでした。')
        return super().form_invalid(form)

【models.py】
from django.db import models
from client.models import Clients
from accounts.models import Users

class Quotations_manager(models.Manager):
    def check_enabled(self):
        return self.filter(is_enabled=True)

class Quotations_details_manager(models.Manager):
    def check_enabled(self):
        return self.filter(is_enabled=True)


class Quotations(models.Model):
    quotation_id = models.AutoField(primary_key=True)
    client_id = models.ForeignKey(Clients, on_delete=models.DO_NOTHING, db_column='client_id')
    username = models.ForeignKey(Users, on_delete=models.DO_NOTHING, db_column='username')
    created_datetime = models.DateTimeField(auto_now_add=True)
    updated_datetime = models.DateTimeField(auto_now=True)
    expiry = models.CharField(max_length=255, blank=True, null=True, default="ご下命後1ヶ月間")
    recipient = models.CharField(max_length=255, blank=True, null=True)
    title = models.CharField(max_length=255, blank=True, null=True)
    delivery_time = models.CharField(max_length=255, blank=True, null=True)
    payment_term = models.CharField(max_length=255, blank=True, null=True)
    consumption_tax = models.IntegerField(default=0)
    remark = models.TextField(blank=True, null=True)
    is_active = models.BooleanField(default=True)

    def __str__(self):
        return self.name

    class Meta:
        verbose_name_plural = "quotations"

    objects = Quotations_manager()

class Quotations_details(models.Model):
    quotation_id = models.ForeignKey(Quotations, on_delete=models.CASCADE, db_column='quotation_id')
    item_id = models.AutoField(primary_key=True)
    merchandise = models.CharField(max_length=255, blank=True, null=True)
    merchandise_description = models.TextField(blank=True, null=True)
    quantity = models.IntegerField(default=0)
    unit = models.CharField(max_length=255, blank=True, null=True)
    sales_unit_price = models.IntegerField(default=0)
    purchase_unit_price = models.IntegerField(default=0)

    def __str__(self):
        return self.name

    class Meta:
        verbose_name_plural = "quotations_details"

    objects = Quotations_details_manager()

【forms.py】
from django import forms
from .models import Quotations, Quotations_details

class QuotationsForm(forms.ModelForm):
    class Meta:
        model = Quotations
        fields = '__all__'

class Quotations_detailsForm(forms.ModelForm):
    class Meta:
        model = Quotations_details
        fields = '__all__'



class RegistrationForm(forms.ModelForm):
    class Meta:
        model = Quotations
        fields = ('quotation_id','client_id','username','expiry','recipient','title','delivery_time','payment_term','consumption_tax','remark')
        labels={
            'client_id':'顧客',
            'username':'作成者',
            'expiry':'見積有効期限',
            'recipient':'宛名',
            'title':'件名',
            'delivery_time':'納期',
            'payment_term':'取引条件',
            'consumption_tax':'消費税額',
            'remark':'備考',
        }


Quotations_details_formSet = forms.inlineformset_factory(
    parent_model = Quotations,
    model = Quotations_details,
    fields = '__all__',#('client_id','username','expiry','recipient','title','delivery_time','payment_term','consumption_tax','remark','merchandise','merchandise_description','quantity','unit','sales_unit_price','purchase_unit_price'),
    extra = 1
)