Use the 'well-known' configuration document to configure the SSO OpenID providers

[gbarbon]

Is your feature request related to a problem? Please describe.
The SSO generic-provider in Kapua requires passing various properties in order to connect properly to the OpenID Provider. However, we could simply read the well-known configuration document provided by the OpenID Provider and configure the generic-provider consequently.

The well-known configuration document is part of the OpenID specification, see here for more information.

Describe the solution you'd like
The configuration step could first try configuring by using the well-known document. Then, if this step fails, it could use the manual configuration.

Describe alternatives you've considered
An alternative could be implementing an automatic-provider dedicated to the automatic configuration through the well-known document and maintain the generic-provider as it is currently implemented for manual configuration.

Additional context
Implementing this improvement does not mean to get rid of dedicated providers, since there can be OpenID Providers that are not fully compliant with the OpenID specification and thus require a dedicated provider to be configured on Kapua.