I had to implement a SP SAML logic at a previous job. The customer who wanted it just kept telling us to enable some apache mod and it works, except when you have a java fat jar without Apache, you have to add your own endpoints and we had to add integration for native clients.

I asked about implementing logout cause I saw it was a thing in the SAML docs. The customer didn't care so our app trashed it cookies as usual and didn't report it to the IdP. It just wasn't worth the time.