Possible memory leak in /enroll process

[natesulat]

While running setup steps in protocol-integration-tests, it was discovered that there was an upper limit to how many fingerprints you could safely enroll using the /v2/kiva/api/guardian/enroll endpoint. (This number fluctuated, but it was never greater than 7 fingerprints.) The bioauth-service simply stopped running after a certain number of enrollments.

After consulting with @jeffk-kiva, the conclusion is that this probably is the result of a memory leak somewhere in the enroll process.

Repro steps:

1. Clone https://github.com/kiva/protocol-integration-tests
2. Add AUTH0_ENABLED=false and FSP_CONTROLLER=http://fsp-controller:3013 to services/gateway/test.env
3. Follow the installation steps in protocol-integration-tests to run the services in Docker, being sure to add --profile frontend to the docker-compose command
4. In a browser window, navigate to http://localhost:7567
5. Once the window loads, click "Accept", then "Fingerprint Registration"
6. Enter a mock e-mail
7. Click each box to add a fingerprint image
8. Open the "Network" tab in your browser's dev tools window
9. Click "Next"

(Note: There's no visual cue that your request has begun or succeeded, so the only way to see the state of your request is via the network tab.)