Display whether escrowed secret is newly created or not

[aysiu]

Details of PR

This obviously isn't necessary for core functionality, but it is just more interesting information to get back when escrowing a key (is it a new key, or are you just escrowing the old one again?).

Testing Done

First time escrowing returns true for newly_created:

NAMEOFHOST:~$ curl -d "serial=ACTUALSERIALNUMB&secret_type=recovery_key&recovery_password=NEWRECOVERYKEY2&username=ACTUALUSERNAME"  http://localhost:8000/checkin/
{"serial": "ACTUALSERIALNUMB", "username": "ACTUALUSERNAME", "rotation_required": false, "newly_created": true}

Subsequent escrows return false:

NAMEOFHOST:~$ curl -d "serial=ACTUALSERIALNUMB&secret_type=recovery_key&recovery_password=NEWRECOVERYKEY2&username=ACTUALUSERNAME"  http://localhost:8000/checkin/
{"serial": "ACTUALSERIALNUMB", "username": "ACTUALUSERNAME", "rotation_required": false, "newly_created": false}
NAMEOFHOST:~$ curl -d "serial=ACTUALSERIALNUMB&secret_type=recovery_key&recovery_password=NEWRECOVERYKEY2&username=ACTUALUSERNAME"  http://localhost:8000/checkin/
{"serial": "ACTUALSERIALNUMB", "username": "ACTUALUSERNAME", "rotation_required": false, "newly_created": false}

Same happens for another key:

NAMEOFHOST:~$ curl -d "serial=ACTUALSERIALNUMB&secret_type=recovery_key&recovery_password=NEWRECOVERYKEY3&username=ACTUALUSERNAME"  http://localhost:8000/checkin/
{"serial": "ACTUALSERIALNUMB", "username": "ACTUALUSERNAME", "rotation_required": false, "newly_created": true}
NAMEOFHOST:~$ curl -d "serial=ACTUALSERIALNUMB&secret_type=recovery_key&recovery_password=NEWRECOVERYKEY3&username=ACTUALUSERNAME"  http://localhost:8000/checkin/
{"serial": "ACTUALSERIALNUMB", "username": "ACTUALUSERNAME", "rotation_required": false, "newly_created": false}

In total, only two key entries: