Bug fix and improved `payload` handling in `http_client_req`.
Changes to `http_client_req` behaviour:
If the user provides `payload_len` it is used to generate the
`Content-Length` header. This is done even if `payload_cb` is used to
provide the actual data. If no `payload_len` is specified then no
`Content-Length` is generated.
If `payload_cb` is provided it is called to send the payload data.
Otherwise `payload` is used as the payload buffer and sent. If
`payload_len` is not zero, it is used as the size of `payload`.
Otherwise `payload` is assumed to be a string and `strlen` is used to
determine its size. This is to maintain current behaviour and not break
existing samples.
Fixes#24431
Signed-off-by: Arvin Farahmand <arvinf@ip-logix.com>
Use k_timeout_t internally, no change to user API.
Clarify the documentation of the timeout parameter that it is
in milliseconds.
Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
