3.4.0

• Update Guzzle tracing middleware to meet the expected standard (#1234)
• Add toArray public method in PayloadSerializer to be able to re-use Event serialization
• The withScope methods now return the callback's return value (#1263)
• Set the event extras by taking the data from the Monolog record's context (#1244)
• Make the StacktraceBuilder class part of the public API and add the Client::getStacktraceBuilder() method to build custom stacktraces (#1124)
• Support handling the server rate-limits when sending events to Sentry (#1291)
• Treat the project ID component of the DSN as a string rather than an integer (#1294)