TF-8697: Support TLS 1.3

[sudomateo]

Closes #263

The Vault health check in Terraform Enterprise utilizes this vault-ruby library. When Terraform Enterprise is configured to communicate with a Vault server that only supports TLS v1.3, the Vault health check fails and Terraform Enterprise fails to start:

# tfe-admin health-check
checking: Archivist Health Check...
|  checks that Archivist is up and healthy
|- ✓ PASS

checking: Terraform Enterprise Health Check...
|  checks that Terraform Enterprise is up and can communicate with Redis and Postgres
|- ✗ ERROR: http://127.0.0.1:9292/_health_check?full did not return a healthy status, 500

checking: Terraform Enterprise Vault Health Check...
|  checks that Terraform Enterprise can connect to Vault and is able to encrypt and decrypt tokens
|- ✓ PASS

checking: Fluent Bit Health Check...
|  checks that the configure Fluent Bit server is healthy
|- SKIPPED

checking: RabbitMQ Health Check...
|  checks that RabbitMQ can be connected to and that we can send and consume messages
|- SKIPPED

checking: Vault Server Health Check...
|  checks that the configured Vault Server is healthy
|- ✓ PASS

1 check failed.

The underlying Atlas logs show more information about the failed Vault health check.

2023-09-13 17:04:40 [INFO] [16965a07-d6cd-42a5-b05c-3f8fa7dadac9] [dd.service=atlas dd.trace_id=3137792820384578439 dd.span_id=0] {"method":"GET","path":"/_health_check","format":"html","status":500,"allocations":77263,"duration":102.29,"view":0.69,"db":0.86,"dd":{"trace_id":"3137792820384578439","span_id":"0","env":"","service":"atlas","version":""},"ddsource":["ruby"],"uuid":"16965a07-d6cd-42a5-b05c-3f8fa7dadac9","remote_ip":"127.0.0.1","request_id":"16965a07-d6cd-42a5-b05c-3f8fa7dadac9","user_agent":"Go-http-client/1.1","user":null,"auth_source":null}
2023-09-13 17:04:42 [INFO] [640e2bed-3071-4009-8a9d-b879b2297ae6] [dd.service=atlas dd.trace_id=4180500942360885713 dd.span_id=0] health_check: Connecting to DB
2023-09-13 17:04:42 [INFO] [640e2bed-3071-4009-8a9d-b879b2297ae6] [dd.service=atlas dd.trace_id=4180500942360885713 dd.span_id=0] health_check: Connecting to Redis
2023-09-13 17:04:42 [INFO] [640e2bed-3071-4009-8a9d-b879b2297ae6] [dd.service=atlas dd.trace_id=4180500942360885713 dd.span_id=0] health_check: Connecting to Vault
2023-09-13 17:04:42 [ERROR] [640e2bed-3071-4009-8a9d-b879b2297ae6] [dd.service=atlas dd.trace_id=4180500942360885713 dd.span_id=0] Health check failure (vault): SSL_connect returned=1 errno=0 peeraddr=10.0.39.200:8200 state=error: tlsv1 alert protocol version
2023-09-13 17:04:42 [INFO] [640e2bed-3071-4009-8a9d-b879b2297ae6] [dd.service=atlas dd.trace_id=4180500942360885713 dd.span_id=0] health_check: Sending 500 response

This pull request replaces the deprecated ssl_version with min_version in order to support TLS v1.3. Previously, the code statically defined the TLS version to TLS v1.2, meaning that this vault-ruby library could not connect to Vault servers that only supported TLS v1.3.

With these changes, the Vault health check passes and Terraform Enterprise can start and perform runs.

root@ip-10-0-58-110:~# tfe-admin health-check
checking: Archivist Health Check...
|  checks that Archivist is up and healthy
|- ✓ PASS

checking: Terraform Enterprise Health Check...
|  checks that Terraform Enterprise is up and can communicate with Redis and Postgres
|- ✓ PASS

checking: Terraform Enterprise Vault Health Check...
|  checks that Terraform Enterprise can connect to Vault and is able to encrypt and decrypt tokens
|- ✓ PASS

checking: Fluent Bit Health Check...
|  checks that the configure Fluent Bit server is healthy
|- SKIPPED

checking: RabbitMQ Health Check...
|  checks that RabbitMQ can be connected to and that we can send and consume messages
|- SKIPPED

checking: Vault Server Health Check...
|  checks that the configured Vault Server is healthy
|- ✓ PASS

  All checks passed.

[averche]

This makes sense to me though I don't have much experience with ruby

[evanphx]