Save `operation_result` and `proposed_ops` as objects in ElasticSearch plugin

[abitmore]

User Story

As a user of ElasticSearch plugin I'd like that the operation_result field can be saved as objects so that the data can be indexed.

And mentioned by @sschiessl-bcp in #2380 (comment):

I also noticed that proposals' proposed ops are stored as string, might be interesting as well

Additional Context (optional)
By now op in ES are saved as objects and strings, but operation_result is only strings.

#1400 is related.

#2568 is the next work to be done.

Impacts
Describe which portion(s) of BitShares Core may be impacted by your request. Please tick at least one box.

• API (the application programming interface)
• Build (the build process or something prior to compiled code)
• CLI (the command line wallet)
• Deployment (the deployment process after building such as Docker, Travis, etc.)
• DEX (the Decentralized EXchange, market engine, etc.)
• P2P (the peer-to-peer network for transaction/block propagation)
• Performance (system or user efficiency, etc.)
• Protocol (the blockchain logic, consensus, validation, etc.)
• Security (the security of system or user data, etc.)
• UX (the User Experience)
• Other (please add below)

CORE TEAM TASK LIST

• Evaluate / Prioritize Feature Request
• Refine User Stories / Requirements
• Define Test Cases
• Design / Develop Solution
• Perform QA/Testing
• Update Documentation

[sschiessl-bcp]

I also noticed that proposals' proposed ops are stored as string, might be interesting as well

[abitmore]

@sschiessl-bcp I guess operation_result and proposed_ops were stored as strings intentionally because ES is unable to correctly store static_variant as is as object. It seems it's not a simple change. I'll look into it to see what's the best we can do.

[sschiessl-bcp]

Thanks, if its too complicated it's not a big issue. Benefit is "only" that it would facilitate searching proposal contents.

[abitmore]

#1400 is related.

[abitmore]

Note: in the current implementation, the string version of proposed_ops is not the same as the original json. Specifically, the operation type 12 should be an integer but not a string.

account_history.id : "2.9.479380"
operation_history.op_object.proposed_ops : [{"op":["12",{"fee":{"amount":100000000,"asset_id":"1.3.0"},"issuer":"1.2.0","asset_to_update":"1.3.113","new_options":{"feed_lifetime_sec":86400,"minimum_feeds":7,"force_settlement_delay_sec":86400,"force_settlement_offset_percent":0,"maximum_force_settlement_volume":200,"short_backing_asset":"1.3.0","extensions":{}},"extensions":[]}]}]

[abitmore]

Done via #2565. Closing.
BTW #2568 is the next work to be done.