Make Hashable not use protobuffs?

[taoeffect]

Problem

Our current solution for dealing with potential JSON hash inconsistency is to use protobuffs that clearly define the order of keys. However, it might not be necessary to do that.

Solution

If we just store in the database the first version of the JSON string that was created, and only use that string from then on, then we don't need to use protobuffs at all because the ordering of keys is set in stone from that point on.

Getting rid of protobuffs would mean:

• A simpler codebase
• A simpler backend (no need to have a table with columns for "version", "parentHash", etc just a pure key/value store)
• A smaller bundle size
• Smaller attack surface
• Can make entries based entirely on SBP calls, which makes for nice integration with Transactions + SBP #320
• Might be able to have a single events.js file instead of two
• (?) While we're at it, should also get rid of confusing classes like export class Action extends Hashable and export class Attribute extends Hashable etc

To do this we would need to send the JSON directly as a string. I.e., instead of:

.send({hash: entry.toHash(), entry: entry.toObject()})

Do:

// .JSON never re-calculates JSON again
.send({hash: entry.hash(), json: entry.JSON()})

One of the downsides to try and mitigate is that currently we get runtime validation of the data that's being sent, and it's clear from the shared/events.js file what (a) the events are, (b) what data they expect.

That clarity should be preserved when closing this issue, perhaps via a JSON validator like ajv.

Potential issues?

Implementing this would mean that the hash can no longer be used to verify the integrity of JS objects. Instead, a JS object is considered "verified" if all of these are true:

• The JSON hashes to the hash
• JSON.parse parsed the JSON
• And the resulting object passes validation by the JSON schema validator

EDIT: Since the signature is detached from the JSON itself, double-check that there are no issues if the parts of the JSON that are outside of that signed part are modified!

For example, is there any issue with replay attacks?

EDIT 2: Should be able to get rid of all the classes and just have it be version-specific selector + data

[taoeffect]

Closed by #431.