Support for Client ID Documents

[michielbdejong]

As per https://github.com/solid/solid-oidc/blob/a5a966c7342da01a57bfb316e5533ea7d82fd245/index.bs#L163-L166

The serialized JSON form of a Client ID Document SHOULD use the normative JSON-LD @context
provided at https://www.w3.org/ns/solid/oidc-context.jsonld such that the resulting
document produces a JSON serialization of an OIDC client registration, per the
definition of client registration metadata from [!RFC7591] section 2.

[michielbdejong]

This also implies that clientId is an IRI which means it doesn't easily fit into routes like

solid-nextcloud/solid/appinfo/routes.php

Lines 13 to 15 in 7162a2c

	['name' => 'page#approval', 'url' => '/sharing/{clientId}', 'verb' => 'GET'],
	['name' => 'page#handleRevoke', 'url' => '/revoke/{clientId}', 'verb' => 'GET'],
	['name' => 'page#handleApproval', 'url' => '/sharing/{clientId}', 'verb' => 'POST'],