v7.5.4

Changelog

e02864f Update CHANGELOG.md for v7.5.4
b809be6 Merge pull request #644 from nyaruka/failed_session_fix
cee3f65 Fix contact mixup in test
2ced148 Merge branch 'main' into failed_session_fix
0456a8f Add ping-pong session test
d6862d9 Merge pull request #645 from nyaruka/easier_testing
e820b2f Add test utility to make it easier to test with imported flows
482d911 Failed sessions should be saved with ended_on set