Use xref anchor id

Signed-off-by: Tran Ngoc Nhan <ngocnhan.tran1996@gmail.com>

docs/modules/ROOT/pages/servlet/authentication/mfa.adoc

@@ -44,14 +44,14 @@ The `@EnableMultiFactorAuthentication` `authorities` property is just a shortcut
 When an `AuthorizationManagerFactory` Bean is available, it is used by Spring Security to create authorization rules, like `hasAnyRole(String)`, that are defined on the `AuthorizationManagerFactory` Bean interface.
 The implementation published by `@EnableMultiFactorAuthentication` will ensure that each authorization is combined with the requirement of having the specified factors.
 
-The `AuthorizationManagerFactory` Bean below is what is published in the previously discussed <<emfa, `@EnableMultiFactorAuthentication` example>>.
+The `AuthorizationManagerFactory` Bean below is what is published in the previously discussed xref:emfa[`@EnableMultiFactorAuthentication` example].
 
 include-code::./UseAuthorizationManagerFactoryConfiguration[tag=authorizationManagerFactoryBean,indent=0]
 
 [[selective-mfa]]
 == Selectively Requiring MFA
 
-We have demonstrated how to configure an entire application to require MFA by using <<emfa, ``@EnableMultiFactorAuthentication``s>> `authorities` property.
+We have demonstrated how to configure an entire application to require MFA by using xref:emfa[``@EnableMultiFactorAuthentication``s] `authorities` property.
 However, there are times that an application only wants parts of the application to require MFA.
 Consider the following requirements:
 
@@ -61,7 +61,7 @@ Consider the following requirements:
 
 In this case, some URLs require MFA while others do not.
 This means that the global approach that we saw before does not work.
-Fortunately, we can use what we learned in <<authorization-manager-factory>> to solve this in a concise manner.
+Fortunately, we can use what we learned in xref:authorization-manager-factory[] to solve this in a concise manner.
 
 Start by specifying `@EnableMultiFactorAuthentication` without any authorities.
 By doing so we enable MFA support, but no `AuthorizationManagerFactory` Bean is published.
@@ -121,7 +121,7 @@ include-code::./AdminMfaAuthorizationManagerConfiguration[tag=authorizationManag
 This instructs `DefaultAuthorizationManagerFactory` that any authorization rule should apply our custom `AuthorizationManager` along with any authorization requirements defined by the application (e.g. `hasRole("ADMIN")`).
 <2> Publish `DefaultAuthorizationManagerFactory` as a Bean, so it is used globally
 
-This should feel very similar to our previous example in <<authorization-manager-factory>>.
+This should feel very similar to our previous example in xref:authorization-manager-factory[].
 The difference is that in the previous example, the `AuthorizationManagerFactories` is setting `DefaultAuthorization.additionalAuthorization` with a built in `AuthorizationManager` that always requires the same authorities.
 
 We can now define our authorization rules which are combined with `AdminMfaAuthorizationManager`.
@@ -138,10 +138,10 @@ If we preferred, we could change our logic to enable MFA based upon the roles ra
 [[raam-mfa]]
 == RequiredAuthoritiesAuthorizationManager
 
-We've demonstrated how we can dynamically determine the authorities for a particular user in <<programmatic-mfa>> using a custom `AuthorizationManager`.
+We've demonstrated how we can dynamically determine the authorities for a particular user in xref:programmatic-mfa[] using a custom `AuthorizationManager`.
 However, this is such a common scenario that Spring Security provides built in support using javadoc:org.springframework.security.authorization.RequiredAuthoritiesAuthorizationManager[] and javadoc:org.springframework.security.authorization.RequiredAuthoritiesRepository[].
 
-Let's implement the same requirement that we did in <<programmatic-mfa>> using the built-in support.
+Let's implement the same requirement that we did in xref:programmatic-mfa[] using the built-in support.
 
 We start by creating the `RequiredAuthoritiesAuthorizationManager` Bean to use.
 
@@ -168,7 +168,7 @@ Our example uses an in memory mapping of usernames to the additional required au
 For more dynamic use cases that can be determined by the username, a custom implementation of javadoc:org.springframework.security.authorization.RequiredAuthoritiesRepository[] can be created.
 Possible examples would be looking up if a user has enabled MFA in an explicit setting, determining if a user has registered a passkey, etc.
 
-For cases that need to determine MFA based upon the `Authentication`, a custom `AuthorizationManger` can be used as demonstrated in <<programmatic-mfa>>.
+For cases that need to determine MFA based upon the `Authentication`, a custom `AuthorizationManger` can be used as demonstrated in xref:programmatic-mfa[].
 
 
 [[hasallauthorities]]
@@ -197,7 +197,7 @@ Can you imagine what it would be like to declare hundreds of rules like this?
 What's more that it becomes difficult to express more complicated authorization rules.
 For example, how would you require two factors and either `ROLE_ADMIN` or `ROLE_USER`?
 
-The answer to these questions, as we have already seen, is to use <<emfa>>
+The answer to these questions, as we have already seen, is to use xref:emfa[]
 
 [[re-authentication]]
 == Re-authentication