Spring Securityでログインページの画面レイアウトをカスタマイズ出来ません。

前提

認証機能では、Form認証とGoogle認証二つを実装しており
実際のlogin画面は、http://localhost:8080/loginになり
Controller.javaにもlogin.htmlを呼び出す実装もしています。

下記の記事を元に作成しました。
https://qiita.com/kazuki43zoo/items/53804e18337933a77ad0

今回のソースコード（GitHub）:
https://github.com/NishiguchiHiroki/TodoApp

実現したいこと

ログイン画面のデフォルト画面を、下記の実装したい画面(login.html)へカスタマイズしたいです。
認証機能は問題なく動いています。

デフォルト画面：

実装したい画面(login.html)：

該当のソースコード

SecurityConfig.java
1package com.example.its.config;
2
3import org.springframework.security.config.annotation.authentication.builders.AuthenticationManagerBuilder;
4import org.springframework.security.config.annotation.web.builders.HttpSecurity;
5import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
6import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
7import org.springframework.security.core.userdetails.UserDetailsService;
8import org.springframework.security.crypto.password.NoOpPasswordEncoder;
9import org.springframework.security.crypto.password.PasswordEncoder;
10
11import com.example.its.domain.auth.CustomUserDetailsService;
12
13import lombok.RequiredArgsConstructor;
14
15@EnableWebSecurity
16@RequiredArgsConstructor
17public class SecurityConfig extends WebSecurityConfigurerAdapter{
18	
19	private final UserDetailsService userDetailsService;
20	private final PasswordEncoder passwordEncoder;
21	
22	@Override
23	protected void configure(HttpSecurity http) throws Exception {
24		http
25				.authorizeRequests().antMatchers("/h2-console/**").permitAll()
26				.and()
27				.csrf().ignoringAntMatchers("/h2-console/**")
28				.and()
29				.headers().frameOptions().disable();
30		http	
31				.authorizeRequests()
32				.mvcMatchers("/login/**").permitAll()
33				.mvcMatchers("/signup/**").permitAll()
34				.mvcMatchers("/users/**").hasAuthority("ADMIN")
35				.anyRequest().authenticated()
36				.and()
37		        .oauth2Login()
38		        .and()
39		        .formLogin()
40		        .usernameParameter("email")
41		        .passwordParameter("password");
42	}
43
44	@Override
45	protected void configure(AuthenticationManagerBuilder auth) throws Exception {
46		auth.userDetailsService(userDetailsService)
47	        .passwordEncoder(passwordEncoder);
48	}
49}

IndexController
1package com.example.its.web;
2
3import org.springframework.stereotype.Controller;
4import org.springframework.web.bind.annotation.GetMapping;
5import org.springframework.web.bind.annotation.PostMapping;
6
7@Controller
8public class IndexController {
9
10    @GetMapping
11    public String index() {
12        return "index";
13    }
14    
15    @GetMapping("/login")
16    public String showLoginForm() {
17    	return "login";
18    }
19    
20    @GetMapping("/logout")
21    public String showLogoutForm() {
22    	return "logout";
23    }
24}

login.html
1<!DOCTYPE html>
2<html xmlns:th="http://www.thymeleaf.org"
3      th:replace="~{fragments/layout :: layout(~{::title}, ~{::body})}">
4<head>
5    <title>ログインページ | 課題管理アプリケーション</title>
6</head>
7<body>
8<h1 class="mt-3">課題管理アプリケーション</h1>
9<div style="color:red" th:if="${param.error}">
10	<p>ユーザ名もしくはパスワードが違います。</p>
11</div>
12<form action="#" th:action="@{/login}" method="post">
13	<div class="mt-3">
14		<label for="usernameInput" class="form-label">メールアドレス</label>
15		<input type="text" id="usernameInput" name="email" class="form-control">
16	</div>
17	<div class="mt-3">
18		<label for="passwordInput" class="form-label">パスワード</label>
19		<input type="password" id="passwordInput" name="password" class="form-control">
20	</div>
21	<div class="mt-3">
22		<button type="submit" class="btn btn-primary">ログイン</button>
23	</div>
24</form>
25
26<button onclick="location.href='http://localhost:8080/login/oauth2/code/google'">Googleでログイン</button>
27</body>
28</html>

CustomUserDetailsService.java
1package com.example.its.domain.auth;
2
3import java.util.Collection;
4import java.util.Collections;
5import java.util.List;
6
7import org.springframework.security.core.GrantedAuthority;
8import org.springframework.security.core.authority.SimpleGrantedAuthority;
9import org.springframework.security.core.userdetails.UserDetails;
10import org.springframework.security.core.userdetails.UserDetailsService;
11import org.springframework.security.core.userdetails.UsernameNotFoundException;
12import org.springframework.stereotype.Service;
13
14import com.example.its.domain.auth.User.Authority;
15
16import lombok.RequiredArgsConstructor;
17
18@Service
19@RequiredArgsConstructor
20public class CustomUserDetailsService implements UserDetailsService{
21	
22	private final UserRepository userRepository;
23	
24	@Override
25	public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
26		
27		return userRepository.findByUsername(username)
28			.map(
29					user -> new CustomUserDetails(
30							user.getEmail(),
31							user.getPassword(),
32							toGrantedAuthorityList(user.getAuthority())
33					)
34			)
35			
36			.orElseThrow(
37					() -> new UsernameNotFoundException(
38							"Given username is not found. (username" + username + ")"
39					)
40			);
41	}
42
43	private List<GrantedAuthority> toGrantedAuthorityList(User.Authority authority) {
44		return Collections.singletonList(new SimpleGrantedAuthority(authority.name()));
45	}
46}

build.gradle
1dependencies {
2	implementation 'org.springframework.boot:spring-boot-starter-jdbc'
3	implementation 'org.springframework.boot:spring-boot-starter-thymeleaf'
4	implementation 'org.springframework.boot:spring-boot-starter-web'
5	developmentOnly 'org.springframework.boot:spring-boot-devtools'
6	testImplementation 'org.springframework.boot:spring-boot-starter-test'
7	compileOnly 'org.projectlombok:lombok'
8	annotationProcessor 'org.projectlombok:lombok'
9	implementation 'org.mybatis.spring.boot:mybatis-spring-boot-starter:2.2.0'
10	runtimeOnly 'com.h2database:h2'
11	implementation 'org.springframework.boot:spring-boot-starter-validation'
12    implementation 'org.springframework.boot:spring-boot-starter-security'
13    implementation 'org.thymeleaf.extras:thymeleaf-extras-springsecurity5'
14    testImplementation 'org.springframework.security:spring-security-test'
15    implementation 'org.mybatis.spring.boot:mybatis-spring-boot-starter:2.0.1'
16    implementation group: 'org.springframework.security', name: 'spring-security-oauth2-client'
17    implementation group: 'org.springframework.security', name: 'spring-security-oauth2-jose'
18  	runtimeOnly 'org.postgresql:postgresql'
19}