Implement/expose conditional put

[deanm0000]

Basically this: https://docs.rs/object_store/0.13.2/object_store/#conditional-put

[kylebarron]

I'm not sure if object-store-python is being maintained anymore, but fwiw you can do that in obstore, see put and PutMode

[deanm0000]

I'm not sure if object-store-python is being maintained anymore, but fwiw you can do that in obstore, see put and PutMode

Oh nice. I saw you referenced this somewhere and didn't look at when the last commit was.