Incoming permissions logs - handle data in invalid format

Currently we produce incoming permissions logs as a JSON, which is prepared in a non-reliable way. If particular characters (for example `"`) will be present in `x-service-name` header, the result JSON will be invalid.

To consider:
1. Fetch serviceName from client certificate SAN URI, instead of a header.
2. Change log format to something simpler than JSON, for example "every field in a new line"
3. Sanitize JSON strings

More information: https://github.com/allegro/envoy-control/pull/152#discussion_r468397992