[BUG] Signatures do not work in Docker environment

[mdziekon]

Problem description

When working in Docker environment (introduced in #251), the signatures generator does not work for any players with their stats already calculated.

Looking at the image directly (instead of on the embedded image, which is broken), the following error is being thrown:

Fatal error: Uncaught Error: Call to undefined function imagettfbbox() in /var/www/html/generate_sig.php:167

Engine details

• Engine version:
  • version X.Y.Z
  • commit 77f8090
• Custom modifications:
  • Yes
  • No
• Environment:
  • local
  • testing (inaccessible from the outside)
  • production (accessible from the outside world)
• Configuration:
  • Game speeds: N/A
  • Debris settings: N/A
  • Any other relevant config entry: N/A

Steps to reproduce

Prerequisites:

• User X exists
• User X has their stats already calculated

Steps to reproduce the behavior:

1. Go to Overview
2. Scroll down to the Signature

Expected behavior

• Signature is being displayed correctly, with all statistics being correctly rendered

Actual behavior

• Signature is broken (invalid image)

Reproduction environment

Game server environment:

• Docker (as described in https://github.com/mdziekon/UniEngine#docker)