Add LDAP AuthenticationManager factory

[eleftherias]

This PR introduces a LdapBindAuthenticationManagerFactory, LdapPasswordComparisonAuthenticationManagerFactory and EmbeddedLdapServerContextSourceFactoryBean which can be used to create an AuthenticationManager that can perform LDAP authentication.

This is an example usage

@Bean
public EmbeddedLdapServerContextSourceFactoryBean contextSourceFactoryBean() {
	EmbeddedLdapServerContextSourceFactoryBean contextSourceFactoryBean =
			EmbeddedLdapServerContextSourceFactoryBean.fromEmbeddedLdapServer();
	contextSourceFactoryBean.setPort(0);
	return contextSourceFactoryBean;
}

@Bean
AuthenticationManager authenticationManager(BaseLdapPathContextSource contextSource) {
	LdapBindAuthenticationManagerFactory factory = new LdapBindAuthenticationManagerFactory(contextSource);
	factory.setUserDnPatterns("uid={0},ou=people");
	factory.setUserDetailsContextMapper(new PersonContextMapper());
	return factory.createAuthenticationManager();
}

It is equivalent to the following configuration

@Bean
UnboundIdContainer ldapContainer() {
	UnboundIdContainer container = new UnboundIdContainer("dc=springframework,dc=org", "classpath:users.ldif");
	container.setPort(0);
	return container;
}

@Bean
ContextSource contextSource(UnboundIdContainer container) {
	int port = container.getPort();
	return new DefaultSpringSecurityContextSource("ldap://localhost:" + port + "/dc=springframework,dc=org");
}

@Bean
BindAuthenticator authenticator(BaseLdapPathContextSource contextSource) {
	BindAuthenticator authenticator = new BindAuthenticator(contextSource);
	authenticator.setUserDnPatterns(new String[] { "uid={0},ou=people" });
	return authenticator;
}

@Bean
LdapAuthenticationProvider authenticationProvider(LdapAuthenticator authenticator) {
	LdapAuthenticationProvider provider = new LdapAuthenticationProvider(authenticator);
	provider.setUserDetailsContextMapper(new PersonContextMapper());
	return provider;
}

Logs and reference documentation will be added in future commits.

[rwinch]

Thanks for the updates. I've provided feedback inline.

[eleftherias]

Updated example usage:

@Bean
public EmbeddedLdapServerContextSourceFactoryBean contextSourceFactoryBean() {
	EmbeddedLdapServerContextSourceFactoryBean contextSourceFactoryBean =
			EmbeddedLdapServerContextSourceFactoryBean.fromEmbeddedLdapServer();
	contextSourceFactoryBean.setPort(0);
	return contextSourceFactoryBean;
}

@Bean
public AuthenticationManager authenticationManager(BaseLdapPathContextSource contextSource) {
	LdapAuthenticationManagerFactory factory = LdapAuthenticationManagerFactory
			.usingBindAuthentication(contextSource);
	factory.setUserDnPatterns("uid={0},ou=people");
	factory.setUserDetailsContextMapper(new PersonContextMapper());
	return factory.createAuthenticationManager();
}

[rwinch]

Thanks for the updates. I've commented inline

[rwinch]

Thanks! It looks good to me 👍

[eleftherias]

Updated example configuration:

@Bean
public EmbeddedLdapServerContextSourceFactoryBean contextSourceFactoryBean() {
	EmbeddedLdapServerContextSourceFactoryBean contextSourceFactoryBean =
			EmbeddedLdapServerContextSourceFactoryBean.fromEmbeddedLdapServer();
	contextSourceFactoryBean.setPort(0);
	return contextSourceFactoryBean;
}

@Bean
AuthenticationManager authenticationManager(BaseLdapPathContextSource contextSource) {
	LdapBindAuthenticationManagerFactory factory = new LdapBindAuthenticationManagerFactory(contextSource);
	factory.setUserDnPatterns("uid={0},ou=people");
	factory.setUserDetailsContextMapper(new PersonContextMapper());
	return factory.createAuthenticationManager();
}

Note: the issue description has also been updated to the latest configuration.