Add Resource Server by default (for mobile clients)

[mraible]

Overview of the feature request

To help make #9276 easier, I think we should include an OAuth 2.0 resource server when the user chooses OIDC for authentication. We already configure a resource server (with audience validation) for microservices, so it'd just be a matter of configuring it for gateways and monoliths.

Adding this feature would involve adding an AuthInfoResource.java that provides an endpoint with OIDC info (issuer and client ID), allowing it to be accessed by anyone, and configuring a resource server that looks for an Authorization header.

Motivation for or Use Case

This would allow Ionic for JHipster and Ignite JHipster to talk to an OIDC-enabled JHipster 6 app w/o installing files or changing security configuration.

Related issues or PR

#9276

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[mraible]

Fixed by #9416.