fog-human-json: human-readable fog-pack values

This crate provides functions to go back and forth between fog-pack and JSON, making it relatively easy for users to view pretty-printed fog-pack values and edit them with existing JSON tooling. A common complaint with binary data formats like fog-pack is that reading them is painful, and lowering that pain with JSON is exactly what this crate is for.

This is not a crate for turning regular JSON into fog-pack data. It uses a number of special string prefixes to encode fog-pack types in JSON, which can interfere with arbitrary JSON-to-fog conversions.

So, what does this actually do for conversion? Well, it takes each fog-pack type and either directly converts it to a corresponding JSON type, or it specially encodes it in a string that starts with $fog-. So a 32-bit floating point value could be specifically encoded as $fog-F32: 1.23. The full list of types is:

• Str: A regular string. This is just prepended so fog-pack strings that start with $fog- won't get caught by the parser.
• Bin: Encodes the binary data as Base64 using the "standard" encoding (bonus symbols of +/, no padding used, padding is accepted when parsing).
• F32Hex / F64Hex: Encodes a binary32/64 IEEE floating-point value in big-endian hex. The fog-to-json process should only do this when writing out a NaN or Infinity.
• F32 / F64 / Int: Prints a standard JSON Number, but includes the type information. This done by telling the converter to do it specifically, by a user adding type information, or by the converter for any F32 value (as serde_json will always use F64 for floating-point).
• Time: Encodes the time as a RFC 3339 formatted string.
• Hash / Identity / StreamId / LockId: Encodes the corresponding primitive as a base58 string (in the Bitcoin base58 style).
• DataLockbox / IdentityLockbox / StreamLockbox / LockLockbox: Encodes the corresponding lockbox as Base64 data, just like with the "Bin" type.

That covers conversion between fog-pack Values and JSON values, but not Documents and Entries. Those are converted into JSON objects with the following key-value pairs:

• Documents:
  • "schema": If present, a $fog-Hash:HASH with the schema.
  • "signer": If present, a $fog-Identity:IDENTITY with the signer's Identity.
  • "compression": If not present, uses default compression. If present and null, no compression is used. If set to a number between 0-255, uses that as the compression level.
  • "data": The document content. Must be present.
• Entries:
  • "parent": Parent document's hash.
  • "key": Entry's string key.
  • "signer": If present, holds the signer's Identity.
  • "compression": If not present, uses default compression. If present and null, no compression is used. If set to a number between 0 & 255, uses that as the compression level.
  • "data": The entry content. Must be present.

When going from JSON to a Document or Entry, if there's a "signer" specified, it will attempt to pull a matching IdentityKey from a provided Vault and use that to reproduce the signature. If it can't, then the conversion will fail.