[draincoder]

Description

nats-py starts fetch(batch>1) with a no_wait request, so it may return available messages before the batch is full or the timeout expires. FastStream previously passed that partial result straight to the handler. Since fetch() does not expose no_wait, FastStream now fetches the remaining messages within one overall timeout and calls the handler when the batch is full or the timeout expires.

Fixes #2219

Type of change

Please delete options that are not relevant.

• Bug fix (a non-breaking change that resolves an issue)

Checklist

• My code adheres to the style guidelines of this project (just lint shows no errors)
• I have conducted a self-review of my own code
• I have made the necessary changes to the documentation
• My changes do not generate any new warnings
• I have added tests to validate the effectiveness of my fix or the functionality of my new feature
• Both new and existing unit tests pass successfully on my local environment by running just test-coverage
• I have ensured that static analysis tests are passing by running just static-analysis
• I have included code examples to illustrate the modifications

[CLAassistant]

All committers have signed the CLA.