fix(serving): fix cannot decode base64 encoded binary data

[cyclimse]

Summary

What's changed?

• Remove the .encode("utf-8") when creating a body from a base64 response

Why do we need this?

• There is a bug when decoding base64, the binary body was encoded in utf-8 which of course was failing with true binary data
• While this code was unit tested, unfortunately, it was tested with a dummy utf-8 string turned into base64, which of course did not trigger the bug as it was a valid utf-8

How have you tested it?

• Fixed unit test to use a non-utf8 binary output
• Tested locally by returning an image ✅

Checklist

• I have reviewed this myself
• There is a unit test covering every change in this PR
• I have updated the relevant documentation

Details