Use webfinger for OIDC parameter discovery

[kaivol]

Closes #811.

Client side implementation of the changes described in https://github.com/opencloud-eu/opencloud/blob/main/docs/adr/0003-oidc-client-config-discovery.md.

Based on #776.

[RichardFevrier]

Did this PR worked for you @kulmann ?

Just tried it without success on my side, when both web + iOS are working perfectly.

I have tested the webfinger with:

curl -L cloud.mydomain.com/.well-known/webfinger?resource=https://cloud.opencloud.test&rel=http://openid.net/specs/connect/1.0/issuer&platform=desktop | jq
  % Total    % Received % Xferd  Average Speed  Time    Time    Time   Current
                                 Dload  Upload  Total   Spent   Left   Speed
  0      0   0      0   0      0      0      0                              0
100    305 100    305   0      0   2324      0                              0
{
  "subject": "https://cloud.opencloud.test",
  "properties": {
    "http://opencloud.eu/ns/oidc/client_id": "OpenCloudDesktop",
    "http://opencloud.eu/ns/oidc/scopes": [
      "openid",
      "profile",
      "email",
      "groups",
      "offline_access"
    ]
  },
  "links": [
    {
      "rel": "http://openid.net/specs/connect/1.0/issuer",
      "href": "https://auth.mydomain.com"
    }
  ]
}

Which returns groups that is mandatory on my setup since Authelia groups binds to OpenCloud roles.

But when the Authelia page appears I can see that groups are not part of the request.

Edit:
debugged it further:

26-04-28 13:38:21:512 [ debug sync.credentials.oauth ]  [ OCC::OAuth::openBrowser ]:    opening browser
26-04-28 13:38:21:512 [ debug sync.credentials.oauth ]  [ isUrlValid ]: Checking URL for validity: QUrl("https://auth.mydomain.com/api/oidc/authorization?response_type=code&client_id=OpenCloudDesktop&redirect_uri=http://127.0.0.1:32979&code_challenge=Kgkj2cHF9MwXPDyTkZETDhc4Pv07hAXBxgSV8DfBhCI&code_challenge_method=S256&scope=openid offline_access email profile&prompt=consent select_account&state=c5bNXSEMgYIazaZ3aMqJjz3mI7SfpbP00YlzmVl-Q2w%3D")
[2] Sandbox: CanCreateUserNamespace() clone() failure: EPERM

You can see that scopes (scope=openid offline_access email profile) doesn't contain groups.

[kaivol]

@RichardFevrier thanks for testing the PR!
I made some changes, so it should work now.

I also bumped the C++ standard version to 23, i hope this is fine.

[RichardFevrier]

Thanks for your work @kaivol I'll test that tomorrow! 🤩