docs: add TOC

Author: kenjis

user_guide_src/source/concepts/http.rst

@@ -9,6 +9,10 @@ concepts behind HTTP is a **must** for all developers that want to be successful
 The first part of this chapter gives an overview. After the concepts are out of the way, we will discuss
 how to work with the requests and responses within CodeIgniter.
 
+.. contents::
+    :local:
+    :depth: 2
+
 What is HTTP?
 *************
 

user_guide_src/source/concepts/mvc.rst

@@ -2,6 +2,10 @@
 Models, Views, and Controllers
 ##############################
 
+.. contents::
+    :local:
+    :depth: 2
+
 Whenever you create an application, you have to find a way to organize the code to make it simple to locate
 the proper files and make it simple to maintain. Like most of the web frameworks, CodeIgniter uses the Model,
 View, Controller (MVC) pattern to organize the files. This keeps the data, the presentation, and flow through the

user_guide_src/source/concepts/security.rst

@@ -15,6 +15,10 @@ identifying the top vulnerabilities for web applications.
 For each, we provide a brief description, the OWASP recommendations, and then
 the CodeIgniter provisions to address the problem.
 
+.. contents::
+    :local:
+    :depth: 1
+
 ************
 A1 Injection
 ************

user_guide_src/source/concepts/structure.rst

@@ -5,6 +5,10 @@ Application Structure
 To get the most out of CodeIgniter, you need to understand how the application is structured, by default, and what you
 can change to meet the needs of your application.
 
+.. contents::
+    :local:
+    :depth: 2
+
 Default Directories
 *******************