The UserId property returns or changes the user identifier
associated with requests sent to the current provider. If this property
is set, the value will be included with requests using the provider's
supported user identification field. Setting this property to an empty
string disables inclusion of a user identifier with requests.
Some providers allow applications to specify a user identifier as
part of the request payload for diagnostics, analytics, rate limiting,
or request tracking. The control will map this value to the appropriate
request field for the selected provider when supported. The interpretation
and handling of this value is entirely provider-specific. Some providers
may ignore the value, impose restrictions on its format or length, or
use it only for internal monitoring and logging purposes.
Applications should avoid including sensitive or personally
identifiable information in the user identifier value unless required
by the provider. User identifier values may be stored in provider logs
or retained for diagnostic and security purposes.
Changing the value of this property affects subsequent requests
and does not modify requests that are already in progress.