custom entityID

[Cantor, Scott]

The IdP does not use its own metadata, not ever, in any way. Behavior is in the configuration (or driven by SP metadata).

As far as the entityID is concerned,

 I wouldn't. I have 120+ cloud integrations. Not a single one uses a different key or entityID, excepting while I was changing my key on an interim basis. Who is telling you to do this?

Relying party overrides contain a responderId property that controls the entityID used. The one in credentials.xml is for a more obscure purpose but if you're defining your own separate credential in that file anyway, it doesn't hurt anything to also override the entityID there.  The p:entityId-ref="entityID" syntax refers to populating it from a bean that takes its value from the idp.properties setting. The same thing is done internally on the RelyingParty parent bean underlying all of the overrides.

-- Scott