DockerClient - methods docs return types + doc gen

Merge branch 'develop'

Merge branch 'develop'

Switching from GuzzleHttp to Symfony's HttpClient

GuzzleHttp -> Symfony/HttpClient

Minimal PHP version: 7.1.3

Tested PHP versions:
 - 7.1
 - 7.2
 - 7.3
 - 7.4
 - 8.0
 - 8.1

Docker API connection via TCP rather than unix socket

Connecting to Docker API via TCP rather than unix socket for security purposes.

This change requires additional actions in the docker configuration to expose the api on a specific local port.

Version change

Container log retrieval - encoding text to UTF-8