Add Postgres TLS monitoring support

[kozlek]

Describe the feature request

Hi,

I would like to monitor the certificate expiration of my Postgres TLS instance using Gatus.
Monitoring connection already works using TCP, but I would like to get the certificate check too.

Both TLS and STARTTLS checks fail when hitting a Postgres TLS only instance.
Based on what I found on the net, it seems Postgres does protocol negotiation before SSL is started.

The openssl project added a special hook to be able to debug Postgres TLS with s_client:

openssl s_client -starttls postgres -connect <my_domain>:5432

Do you think it would be possible to implement a special handler for the Postgres + TLS protocol ?

Why do you personally want this feature to be implemented?

I had recently an outage due to an expired Postgres certificate and it took me some time to notice it.
I decided to set up a status page and I choose Gatus as it's both simple and featureful 🚀

How long have you been using this project?

1 month

Additional information

No response