Support SSL to expose metrics

[vmercierfr]

Is your feature request related to a problem? Please describe.

A Qonto partner has requested that metrics be exposed via HTTPS.

Describe the solution you'd like

We should be able to support HTTPS when certificate and private keys are specified.

Describe alternatives you've considered

n/a

Additional context

• https://gist.github.com/denji/12b3a568f092ab951456