This change removes the wrapping of the created field in the put user
response. The created field was added as a top level field in #32332,
while also still being wrapped within the `user` object of the
response. Since the value is available in both formats in 6.x, we can
remove the wrapped version for 7.0.
This commit adds a security client to the high level rest client, which
includes an implementation for the put user api. As part of these
changes, a new request and response class have been added that are
specific to the high level rest client. One change here is that the response
was previously wrapped inside a user object. The plan is to remove this
wrapping and this PR adds an unwrapped response outside of the user
object so we can remove the user object later on.
See #29827