Add PSR3 support for logging, instead of syslog/error_log

[jaugustin]

🎟️ Fixes issue 55
📜 Design Doc: link if applicable

Motivation and Context

Adds flexible, standardized SDK logging via PSR-3 so integrators can route logs (including exception context) to their preferred systems. This improves observability and debugging without relying on syslog/error_log.

Description

• Added PSR-3 dependency and a new optional logger argument on EppoClient::init and EppoClient::createTestClient.
• Switched SDK internals (poller/config loader/store) to LoggerAwareTrait and propagate the logger from the client.
• Replaced internal syslog/error_log calls with PSR-3 calls in SDK runtime paths.
• Documented how to keep legacy syslog behavior using a PSR-3 logger (e.g., Monolog SyslogHandler).

How has this been documented?

Updated README initialization options to include the new PSR-3 logger and a note on using Monolog SyslogHandler.

How has this been tested?

Unit test executed

Breaking Change?

Yes. This introduces a new dependency on psr/log and modifies initialization signatures; treat as a major version bump.

[jaugustin]

This is a first version, there is still 2 syslog call in src/DTO/Bandit/AttributeSet.php and src/DTO/Bandit/Bandit.php but I didn't find a good solution for them.

Options are:

• inject PSR log in construct or static method, but as they are not services, if feel very wrong, and push burden on the user
• remove the syslog in those DTO
• keep as is
• Set the Logger in EppoClient as static, so it could be used in static context

What do you think ?

[leoromanovsky]

@jaugustin Thanks for submitting this; I pushed some adjustments, including to your question. How does it look? Please tag me directly for a quickly response.

[jaugustin]

@leoromanovsky changes looks good 👍