documentation around how the pipeline handles errors (retryable and non-retryable errors)

[shashank10456]

Summary

What change needs making?

Documentation around how the pipeline handles errors (retryable and non-retryable errors).

Use Cases

When would you use this?

This will help in understanding the platform better and help the developers in handling the retryable errors in a better way without panicking.

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Message from the maintainers:

If you wish to see this enhancement implemented please add a 👍 reaction to this issue! We often sort issues this way to know what to prioritize.

[vigith]

With the new gRPC-based UDF, a user-defined error cannot be returned to the SDK. The numaflow framework will retry any internal error, and the UDF author should retry the errors within the UDF.