* [core] Add SWITCH_CAUSEs for STIR/SHAKEN.
[mod_sofia] Add sofia_verify_identity dialplan APP as a STIR/SHAKEN verification service. Set sip_hangup_on_verify_identity_fail=true to end calls that fail verification, otherwise check sip_verstat and sip_verstat_detailed channel variables for verification result.
* [mod_sofia] Fix stir shaken implementation issues on fail.
* fix build
* Fix given comments
* stir_shaken_passport_get_grant return does not require to be freed.
* reworked things
* [core] add switch_rfc822_datetime_to_epoch()
* [mod_sofia] fix test return code
* [mod_sofia] Add Date header when signing Identity
* [mod_sofia] Check Date - WIP doesn't work
* [mod_sofia] STIR/SHAKEN check SIP Date header
* Try to give time for sofia to clean up calls
Co-authored-by: Andrey Volk <andywolk@gmail.com>
