feat(api): allow Device Authorization Grant using custom login UI (#9387)

# Which Problems Are Solved

The OAuth2 Device Authorization Grant could not yet been handled through
the new login UI, resp. using the session API.
This PR adds the ability for the login UI to get the required
information to display the user and handle their decision (approve with
authorization or deny) using the OIDC Service API.

# How the Problems Are Solved

- Added a `GetDeviceAuthorizationRequest` endpoint, which allows getting
the `id`, `client_id`, `scope`, `app_name` and `project_name` of the
device authorization request
- Added a `AuthorizeOrDenyDeviceAuthorization` endpoint, which allows to
approve/authorize with the session information or deny the request. The
identification of the request is done by the `device_authorization_id` /
`id` returned in the previous request.
- To prevent leaking the `device_code` to the UI, but still having an
easy reference, it's encrypted and returned as `id`, resp. decrypted
when used.
- Fixed returned error types for device token responses on token
endpoint:
- Explicitly return `access_denied` (without internal error) when user
denied the request
  - Default to `invalid_grant` instead of `access_denied`
- Explicitly check on initial state when approving the reqeust
- Properly handle done case (also relates to initial check) 
- Documented the flow and handling in custom UIs (according to OIDC /
SAML)

# Additional Changes

- fixed some typos and punctuation in the corresponding OIDC / SAML
guides.
- added some missing translations for auth and saml request

# Additional Context

- closes #6239

---------

Co-authored-by: Tim Möhlmann <tim+github@zitadel.com>

internal/static/i18n/de.yaml

@@ -543,6 +543,7 @@ Errors:
     AlreadyExists: Auth Request existiert bereits
     NotExisting: Auth Request existiert nicht
     WrongLoginClient: Auth Request wurde von einem anderen Login-Client erstellt
+    AlreadyHandled: Auth Request wurde bereits bearbeitet
   OIDCSession:
     RefreshTokenInvalid: Refresh Token ist ungültig
     Token:
@@ -553,8 +554,12 @@ Errors:
     AlreadyExists: SAMLRequest existiert bereits
     NotExisting: SAMLRequest existiert nicht
     WrongLoginClient: SAMLRequest wurde con einem andere Login-Client erstellt
+    AlreadyHandled: SAMLRequest wurde bereits bearbeitet
   SAMLSession:
     InvalidClient: SAMLResponse wurde nicht für diesen Client ausgestellt
+  DeviceAuth:
+    NotFound: Die Geräteautorisierungsanforderung existiert nicht
+    AlreadyHandled: Die Geräteautorisierungsanforderung wurde bereits bearbeitet
   Feature:
     NotExisting: Feature existiert nicht
     TypeNotSupported: Feature Typ wird nicht unterstützt