Django ページング機能の追加方法

###前提
Python3.8.3、Django2.2.16でブログアプリを作成しております。

###実現したいこと
ページング参考サイト
上記参考サイトを元にページング機能を追加を追加したいと考えております。

一度ページング機能だけのアプリを作成して上手くいったので、元々作っていたブログアプリに適用させたのですがページング機能らしきものが表示されずエラーも出てきません。

お手数ですがコードの誤りをご指摘いただきたくお願い致します。
（参考サイトではListView等の汎用ビューを使っているものの、ブログアプリでは内容理解のため敢えて汎用ビューをViewのみに限定しております。そこに問題があるのではと予想しているのですが・・・）

###コード
最低限のコードを記載したつもりです。必要以上に削ってしまっていたら恐縮です。
urls.py

python
1from django.urls import path
2from app import views
3
4urlpatterns = [
5    path('', views.IndexView.as_view(), name='index'),
6    path('post/<int:pk>/', views.PostDetailView.as_view(), name='post_detail'),
7    path('post/new/', views.CreatePostView.as_view(), name='post_new'),
8    path('post/<int:pk>/edit/', views.PostEditView.as_view(), name='post_edit'),
9    path('category/<str:category>/', views.CategoryView.as_view(), name='category'),
10    path('category/<str:category>/', views.CategoryNameView.as_view(), name='category_name'),

views.py

python
1from django.views.generic import View
2from django.views.generic.list import MultipleObjectMixin
3from django.shortcuts import render,redirect
4from .models import Post
5from .forms import PostForm
6from django.contrib.auth.mixins import LoginRequiredMixin
7
8class IndexView(View, MultipleObjectMixin):
9    def get(self, request, *args, **kwargs):
10        post_data = Post.objects.order_by("-id")
11        paginate_by = 4
12        return render(request, 'app/index.html', {
13            'post_data': post_data,
14        })
15
16class PostDetailView(View):
17    def get(self, request, *args, **kwargs):
18        post_data = Post.objects.get(id=self.kwargs['pk'])
19        return render(request, 'app/post_detail.html', {
20            'post_data': post_data
21        })
22
23class CreatePostView(LoginRequiredMixin, View):
24    def get(self, request, *args, **kwargs):
25        form = PostForm(request.POST or None)
26        return render(request, 'app/post_form.html', {
27            'form': form
28        })
29    
30    def post(self, request, *args, **kwargs):
31        form = PostForm(request.POST or None)
32
33        if form.is_valid():
34            post_data = Post()
35            post_data.author = request.user
36            post_data.title = form.cleaned_data['title']
37            category = form.cleaned_data['category']
38            post_data.category = Category.objects.get(name=category)
39            post_data.content = form.cleaned_data['content']
40            if request.FILES:
41                post_data.image = request.FILES.get('image')
42            return render(request, 'app/post_preview.html', {
43                'post_data' : post_data
44            })
45
46        return render(request, 'app/post_form.html', {
47            'form': form
48        })
49
50class PostEditView(LoginRequiredMixin, View):
51    def get(self, request, *args, **kwargs):
52        post_data = Post.objects.get(id=self.kwargs['pk'])
53        form = PostForm(
54            request.POST or None,
55            initial={
56                'title': post_data.title,
57                'category': post_data.category,
58                'content': post_data.content,
59                'image': post_data.image,
60            }
61        )
62
63        return render(request, 'app/post_form.html', {
64            'form': form
65        })
66    
67    def post(self, request, *args, **kwargs):
68        form = PostForm(request.POST or None)
69
70        if form.is_valid():
71            post_data = Post.objects.get(id=self.kwargs['pk'])
72            post_data.title = form.cleaned_data['title']
73            category = form.cleaned_data['category']
74            category_data = Category.objects.get(name=category)
75            post_data.category = category_data
76            post_data.content = form.cleaned_data['content']
77            if request.FILES:
78                post_data.image = request.FILES.get('image')
79            post_data.save()
80            return redirect('post_detail', self.kwargs['pk'])
81
82        return render(request, 'app/post_form.html', {
83            'form': form
84        })
85
86
87class CategoryNameView(View):
88    def get(self, request, *args, **kwargs):
89        category_data = Category.objects.get(name=self.kwargs['category'])
90        post_data = Post.objects.filter(category=category_data)
91        return render(request, 'app/index.html', {
92            'post_data' : post_data
93        })

models.py

python
1from django.conf import settings
2from django.db import models
3from django.utils import timezone
4
5class Category(models.Model):
6    name = models.CharField("カテゴリ", max_length=100)
7
8    def __str__(self):
9        return self.name
10class Post(models.Model):
11    author = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
12    category = models.ForeignKey(Category, verbose_name='カテゴリ', on_delete=models.CASCADE)
13    title = models.CharField("タイトル", max_length=200)
14    image = models.ImageField(upload_to='images', verbose_name='Image画像', null=True, blank=True)
15    content = models.TextField("本文")
16    created = models.DateTimeField("作成日", default=timezone.now)
17
18    def __str__(self):
19        return self.title

index.html

html
1{% extends "app/base.html" %}
2{% load static %}
3
4{% block content %}
5<header class="masthead">
6    <div class="container h-100">
7        <div class="row h-100 align-items-center">
8            <div class="col-12 text-center TDL-table">
9                <img src="{% static 'img/TDL.png' %}" alt="">
10            </div>
11        </div>
12    </div>
13</header>
14
15<div class="row my-4">
16
17</div>
18    
19{% for post in post_data %}
20<div class="row">
21    <div class="col-md-4">
22        <a href="#">
23        {% if post.image %}
24            <img class="img-fluid rounded mb-3 mb-md-0" src="{{ post.image.url }}" alt="">
25        {% endif %}
26        </a>
27    </div>
28    <div class="col-md-8">
29        <div class="author-created">
30            <h7 class="text_left">{{ post.author }}</h7>
31            <h7 class="text_right">{{ post.created }}</h7>
32        </div>
33        <h3>{{ post.title }}</h3>
34        <p>{{ post.content|truncatechars:100 }}</p>
35        <a style="float:right;" href="{% url 'post_detail' post.id %}">続きを読む</a>
36    </div>
37</div>
38<hr>
39{% endfor %}
40<div class="text-right">
41    {% include "app/snippets/posts.html" %}
42    {% include "app/pagination.html" %}
43    <a href="{% url 'post_new' %}" class="btn btn-info">新しい記事を投稿</a>
44</div>
45{% endblock %}
46

pagination.html

html
1{% if is_paginated %}
2<nav aria-label="Page navigation">
3    <ul class="pagination justify-content-center">
4        {% if page_obj.has_previous %}
5        <li class="page-item">
6            <a href="?page={{ page_obj.previous_page_number }}" class="page-link" aria-label="Previous">
7                <span aria-hidden="true">&laquo;</span>
8                <span class="sr-only">Previous</span>
9            </a>
10        </li>
11        {% endif %}
12        {% for num in paginator.page_range %}
13        {% if page_obj.number == num %}
14        <li class="page-item active">
15            <span class="page-link">
16                {{ num }}
17                <span class="sr-only">(current)</span>
18            </span>
19        </li>
20        {% else %}
21        <li class="page-item">
22            <a href="?page={{ num }}" class="page-link">{{ num }}</a>
23        </li>
24        {% endif %}
25        {% endfor %}
26        {% if page_obj.has_next %}
27        <li class="page-item">
28            <a class="page-link" href="?page={{ page_obj.next_page_number }}" aria-label="Next">
29                <span aria-hidden="true">&raquo;</span>
30                <span class="sr-only">Next</span>
31            </a>
32        </li>
33        {% endif %}
34    </ul>
35</nav>
36{% endif %}

snippets/posts.html

html
1{% for post in object_list %}
2<div class="card mb-3">
3  <h5 class="card-header">
4    <a href="{{ post.get_absolute_url }}">{{ post.title }}</a>
5  </h5>
6  <div class="card-body">
7    {{ post.content }}
8  </div>
9</div>
10{% endfor %}