NewDataBlob silently swallows encoding type errors instead of returning them to callers

Summary

NewDataBlob in data_blob.go silently ignores invalid
encoding type strings by setting ENCODING_TYPE_UNSPECIFIED
instead of surfacing the error to callers.

Root Cause

func NewDataBlob(data []byte, encodingTypeStr string) *commonpb.DataBlob {
    encodingType, err := enumspb.EncodingTypeFromString(encodingTypeStr)
    if err != nil {
        // TODO: return an UnknownEncodingType error
        encodingType = enumspb.ENCODING_TYPE_UNSPECIFIED  // silent failure
    }
    return &commonpb.DataBlob{...}
}

Impact

• Invalid encoding type strings fail silently
• Error only surfaces later during deserialization
• Harder to diagnose root cause of encoding failures
• No signal to caller that something went wrong at creation time

Suggested Fix

Change function signature to return (*commonpb.DataBlob, error)
and return error when encoding type is invalid. Alternatively,
add a separate NewDataBlobWithError variant that callers can
use when they need error handling.

Question for team

Should this be a signature change (breaking) or a new function
variant? How many callers need updating?

References

• common/persistence/data_blob.go:9