retry: Allow setup of buffer for request body if GetBody property…

[robbieheywood]

Changes

• Add the ability for the retry tripperware to setup buffers that can be used to read the request body multiple times if it doesn't have a GetBody property.
• Add an option to allow turning the above behaviour on.
• Testing updated

Verification

Retry tripperware integration tests added to and passing

[bwplotka]

Hey, so recently we add this to kEdge, wonder if we can do similar here without extra option?

improbable-eng/kedge#152

What do you think?

[robbieheywood]

Hey, so recently we add this to kEdge, wonder if we can do similar here without extra option?

improbable-eng/kedge#152

What do you think?

Ah interesting, thanks for pointing out! I added the option to be conservative (it's opt-in) but would be happy to just make this the default if you think that's better?

[bwplotka]

Relying on GetBody might be misleading that's why we added the resetable, buffered reader (:
We found it quite stable, so I would try to make it a default, especially if you want to do it only for certain edge cases like no GetBody - but up to you.