Nano-node: Replace JSON library

[cryptocode]

The current use of Boost ptree in RPC is problematic for several reasons:

• The output is not standard JSON
  
  
  
  • Empty objects and arrays are replaced with strings
  
  
  • Bool values are quoted
  
  
  • Numbers are quoted. However, arbitrary precision numbers (such as balances) should still be quoted. This is fairly common practice because several JSON parsers otherwise fail or give the wrong result.
  
  
• Slow and memory hungry
• No streaming/sax support. We may want to employ this in the future for more efficient handling of large requests/responses.

Challenges/notes:

• Just replacing the library would be a breaking change. The approach will be to make the JSON backend configurable. We can deprecate Boost ptree, but keep it default for a while.
• It's a large change, as it touches all RPC actions and block-json serializations.
  
  
  
  • Step 1 is to make an internal library, e.g a common interface which can have multiple implementations.
    
    
    
    
    
    • Implement Boost ptree backend
    
    
    
    • Implement RapidJSON backend (RapidJSON will likely be a git submodule)
    
    
    
  
  
  • Step 2 is to replace all use of Boost ptree with the internal library.
    
    
    
    
    
    • RPC
    
    
    
    • Block serialization
    
    
    
    • Config file?
    
    
    
    • This step depends on https://github.com/nanocurrency/nano-node/issues/1827
    
    
    
  
  

This replaces a few related issues.

[kolya182]

Awaiting for a fix https://github.com/trustwallet/blockatlas/blob/master/platform/nano/model.go#L18

[cryptocode]

@kolya182 out of curiosity, would your Go client deal with both history being an empty array [] and history not being present at all in the JSON?

[kolya182]

@kolya182 out of curiosity, would your Go client deal with both history being an empty array [] and history not being present at all in the JSON?

Empty array is expected for address with 0 transactions, instead history returns different type. Expecting to have history property no matter amount of transactions would be ideal.

[zhyatt]

In V22 flatbuffers' JSON support takes over ptree with RPC 2.0. Migration to the new RPC version will remove this issue.