[CDEC-462] Add `ToJSON` instance for `InvReqDataFlowLog`
[CDEC-462] Add `ToJSON` instance for `InvReqDataFlowLog`

input-output-hk/cardano-sl,input-output-hk/pos-haskell-prototype,input-output-hk/cardano-sl,input-output-hk/pos-haskell-prototype,input-output-hk/cardano-sl,input-output-hk/cardano-sl,input-output-hk/pos-haskell-prototype