Fix #1871

[achamayou]

Fix #1871

41: 16:54:14.612 | INFO     | infra.member:update_ack_state_digest:142 - [0|member0] POST /gov/ack/update_state_digest
41: 16:54:14.612 | INFO     | infra.member:update_ack_state_digest:142 - 200 @2.4 {"state_digest":"2fb5520d4d50d599f056378925de1208e2a88b81666a5cd75e1ca1ff978b8ed6"}

[ghost]

fix_update_state_digest_schema@15406 aka 20201113.13 vs master ewma over 50 builds from 14843 to 15395

[achamayou]

After discussion with @jumaffre, I'm wrapping this again in a top-level JSON object, under a single key. I think we want to apply the following principles across all node and governance RPCs:

• JSON in/out, by default. We may accept, and return (given the right Accept:) other content types for convenience, but JSON should always be available, for:
  • Consistency when scripting/interacting from code.
  • Extensibility, adding new fields to an object is straightforward.
• Digests are always encoded as hex-strings in JSON
• Where we need to embed other binary values, such as quotes or requests, in JSON, they will be encoded as base64

[jumaffre]

Is it possible to do return make_success(ma->state_digest); instead of constructing a JSON object?

[achamayou]

No, because the serialisation auto-unwraps state_digest, so that ends up being just a string.