feat: explicitly specify containerPort in helm chart

[hsudbrock]

Fixes #1305

Description

Currently, the deployment from the connaisseur helm chart does not explicitly specify the containerPort. This is usually not a problem, because the port can still be used, even if it is not explicitly named.

Explicitly specifying the port has two benefits:

• It documents the available ports for a user of the chart.
• It enables to configure automatic scraping of metrics by prometheus using a PodMonitor from the prometheus operator (which requires the port to be explicitly specified). This helps in working around the issue described in Prometheus cannot connect to /metrics HTTPS endpoint #709, to scrape metrics even when they are provided via https only.

In principle, one could also name the port, but since there is only one exposed port and I did not want to use a generic name like thePort, I did not add a port name.

Checklist

• [ x] PR is rebased to/aimed at branch develop
• [ x] PR follows Contributing Guide
• [ x] Added tests (if necessary)
• [ x] Extended README/Documentation (if necessary)
• [ x] Adjusted versions of image and Helm chart in Chart.yaml (if necessary)

[phbelitz]

merged in #1308, thank you @hsudbrock