✨ feat(envoy-proxy): Enable access logging for HTTP requests

[olivier97]

HTTP request logging

Goal

We want to be able to better track what has happened (and when). This PR enables us to do just that - access logs are written to stdout.

Example: Command injection (via proxy-service)

Command executed:

$ ug-exploit cmd-inject-proxy "echo test"

The envoy-proxy logs can then for example be retrieved as follows:

$ kubectl -n unguard logs <name of envoy proxy pod>

Matching log line (formatted for better readability):

{
    "response_code": 500,
    "downstream_remote_address": "...",
    "timestamp": "2023-11-15T13:48:12.118Z",
    "payload": "imgurl=example.com+%26%26+echo+test+%23",
    "content_type": "application/x-www-form-urlencoded",
    "hostname": "unguard-envoy-proxy-6fcbb8ddf4-92b9m",
    "message": "",
    "upstream_remote_address": "...",
    "user_agent": "python-requests/2.28.2",
    "original_path": "/ui/post",
    "response_code_details": "via_upstream"
}

As can be seen in the log line above, the command we've attempted to inject (echo test) has been logged as well as the time stamp, the content type of the request etc.