feat: AssignmentTrackingProvider used to track local evaluation assignment events

[tyiuhc]

Summary

• AssignmentTrackingProvider interface

  • Implementation needs to be passed to AssignmentConfig to send assignment events from local evaluations to Amplitude
  • The track method takes in an Assignment object, which represents an assignment event
  • Sending an event to Amplitude
    • see developer docs for more details
    • Assignment::toJSONPayload can be used to convert an Assignment to a JSON string representation of the payload required to send an event to Amplitude
    • Assignment::toJSONString can be used to convert an Assignment to a JSON string representation of an assignment event - this is equivalent to an object in the events array in the payload

• DefaultAssignmentTrackingProvider

  • A default implementation of the AssignmentTrackingProvider interface which uses the synchronous internal Amplitude package
  • Recommended for use of testing and applications where latency is less of a concern

• Refactors

  • minIdLength (minimum permitted length for user_id and device_id fields for assignment event) added to AssignmentConfig
  • Internal Amplitude package is no longer automatically used to send assignment events
  • logger added to AmplitudeConfig instead of being passed via LocaEvaluationClient
  • toEvent moved from AssignmentService to Assignment

[marco-perrullo]

On PR summary comment you mention that we could do Assignment::toJSONPayload or Assignment::toJSONString but this methods are not static so I guess that we should do something like:

$assignment = new Assignment($user,$variants,$apiKey);
$assignment->toJSONString();

Is this correct?

[tyiuhc]

On PR summary comment you mention that we could do Assignment::toJSONPayload or Assignment::toJSONString but this methods are not static so I guess that we should do something like:

$assignment = new Assignment($user,$variants,$apiKey);
$assignment->toJSONString();

Is this correct?

Yes, that is correct.

[github-actions[bot]]

:tada: This PR is included in version 0.5.0 :tada:

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