fix: provide device auth config (#8419)

# Which Problems Are Solved

There was no default configuration for `DeviceAuth`, which makes it
impossible to override by environment variables.
Additionally, a custom `CharAmount` value would overwrite also the
`DashInterval`.

# How the Problems Are Solved

- added to defaults.yaml
- fixed customization

# Additional Changes

None.

# Additional Context

- noticed during a customer request

cmd/defaults.yaml

@@ -358,6 +358,13 @@ OIDC:
       Path: /oauth/v2/keys # ZITADEL_OIDC_CUSTOMENDPOINTS_KEYS_PATH
     DeviceAuth:
       Path: /oauth/v2/device_authorization # ZITADEL_OIDC_CUSTOMENDPOINTS_DEVICEAUTH_PATH
+  DeviceAuth:
+    Lifetime: 5m # ZITADEL_OIDC_DEVICEAUTH_LIFETIME
+    PollInterval: 5s # ZITADEL_OIDC_DEVICEAUTH_POLLINTERVAL
+    UserCode:
+      CharSet: "BCDFGHJKLMNPQRSTVWXZ" # ZITADEL_OIDC_DEVICEAUTH_USERCODE_CHARSET
+      CharAmount: 8 # ZITADEL_OIDC_DEVICEAUTH_USERCODE_CHARARMOUNT
+      DashInterval: 4 # ZITADEL_OIDC_DEVICEAUTH_USERCODE_DASHINTERVAL
   DefaultLoginURLV2: "/login?authRequest=" # ZITADEL_OIDC_DEFAULTLOGINURLV2
   DefaultLogoutURLV2: "/logout?post_logout_redirect=" # ZITADEL_OIDC_DEFAULTLOGOUTURLV2
   PublicKeyCacheMaxAge: 24h # ZITADEL_OIDC_PUBLICKEYCACHEMAXAGE

internal/api/oidc/device_auth.go

@@ -60,7 +60,7 @@ func (c *DeviceAuthorizationConfig) toOPConfig() op.DeviceAuthorizationConfig {
 		out.UserCode.CharAmount = c.UserCode.CharAmount
 	}
 	if c.UserCode.DashInterval != 0 {
-		out.UserCode.DashInterval = c.UserCode.CharAmount
+		out.UserCode.DashInterval = c.UserCode.DashInterval
 	}
 	return out
 }