Support configuration of localEntityIdTemplate for a SAML Relying Party

[danilopiazza]

Hi, this PR fixes #20352 by adding support for auto-configuring RelyingPartyRegistration.localEntityIdTemplate.

Support for the new property has been added to the top-level Registration class, as suggested by @mbhave in #20352 (comment).

[wilkinsona]

Thanks very much for the PR, @danilopiazza. I left a few comments. When you have a moment, please take a look and let us know what you think.

[danilopiazza]

@wilkinsona localEntityIdTemplate is going to be deprecated in Spring Security 5.4 in favour of entityId: spring-projects/spring-security@8e8a642.

Should I update this PR to use the new property (possibly changing the configuration property name from local-entity-id-template to relying-party-entity-id), or is 2.4.x going to be compatible with Spring Security 5.3?

[wilkinsona]

Thanks for joining the dots there, @danilopiazza. Spring Boot 2.4 will require Spring Security 5.4 so let's switch to relying-party-entity-id please.

[danilopiazza]

Thanks for joining the dots there, @danilopiazza. Spring Boot 2.4 will require Spring Security 5.4 so let's switch to relying-party-entity-id please.

I am still calling RelyingPartyRegistration#getLocalEntityIdTemplate and RelyingPartyRegistration.Builder#localEntityIdTemplate because current master depends on Spring Security 5.4.0-M1, where the new methods are not available yet.

(As a side note: should I open another PR after rebasing on current master and squashing commits?)

[wilkinsona]

current master depends on Spring Security 5.4.0-M1

Please feel free to switch to 5.4.0-SNAPSHOT in this PR. 5.4.0-RC1 will be released in time for Spring Boot 2.4.0-M2 so we can switch to snapshots now and then pick up RC1 when it's released.

should I open another PR after rebasing on current master and squashing commits?

No need for another PR, thanks. You can just force-push this one.

[danilopiazza]

No need for another PR, thanks. You can just force-push this one.

Done! I force-pushed two separate commits: one to upgrade the Spring Security dependency, and another one with the PR changes.

[snicoll]

@danilopiazza thank you very much for making your first contribution to Spring Boot.