* User registration is controled by #LinphoneProxyConfig settings.<br> Each #LinphoneProxyConfig object can be configured with registration informations
* like \link linphone_proxy_config_set_server_addr() proxy address \endlink , \link linphone_proxy_config_set_identity() user id \endlink, \link linphone_proxy_config_expires()
* like \link linphone_proxy_config_set_server_addr() proxy address \endlink , \link linphone_proxy_config_set_identity_address() user id \endlink, \link linphone_proxy_config_expires()
* refresh period \endlink, and so on.
* <br> A created proxy config using linphone_proxy_config_new(), once configured, must be added to #LinphoneCore using function linphone_core_add_proxy_config().
* <br> It is recommended to set a default \link #LinphoneProxyConfig proxy config \endlink using function linphone_core_set_default_proxy(). Once done, if \link #LinphoneProxyConfig
* <br> A created proxy config using linphone_core_create_proxy_config(lc), once configured, must be added to #LinphoneCore using function linphone_core_add_proxy_config().
* <br> It is recommended to set a default \link #LinphoneProxyConfig proxy config \endlink using function linphone_core_set_default_proxy_config(). Once done, if \link #LinphoneProxyConfig
* a proxy config \endlink has been configured with attribute \link linphone_proxy_config_enable_register() enable register \endlink , next call to linphone_core_iterate() triggers
* a SIP register.
* <br> Registration status is reported by LinphoneCoreRegistrationStateChangedCb.