[LSP2] Tuple encoding

[JeneaVranceanu]

We have the following tuple examples in the LSP2 standard:

These examples are valid and work both ways - encoding and decoding.
But using tuples like (address,bytes,string) or (bytes,bytes,bytes8) or anything where we have a dynamic type in any but the last position will not work because values are just "glued together".

And even though we can make this (bytes,bytes8) work by taking last 8 bytes as bytes8 and the rest as bytes it doesn't make sense when it comes to implementation of deocding.

Example:

type = (bytes,string)
values1 = (0xcafe,"not really a cafe, is it?")
values2 = (0xbeeeeeeeeeeeeeef,"some people just love it")

... doing encoding ...

values1Encoded = 0xcafe6e6f74207265616c6c79206120636166652c2069732069743f
values2Encoded = 0xbeeeeeeeeeeeeeef736f6d652070656f706c65206a757374206c6f7665206974

/// ERROR: where in these long blobs the first values start and the second end?
decodeLsp2Values(type, values1Encoded)
decodeLsp2Values(type, values2Encoded)

I suggest we either fallback to using Solidity's way of encoding tuples or add the same 2 bytes for the length of each value (as we have in the CBAs) in the tuple, or even better we use the following idea suggested by @skimaharvey: #172 (comment)

The idea is to have 1 byte that will hold the length of the length of the element, the next 1 or more bytes that describe the length of the element and the next 1 or more bytes should be the element itself:

Using that idea tuples will be encoded in the following manner:

type = (bytes,string)
values1 = (0xcafe,"not really a cafe, is it?")
values2 = (0xbeeeeeeeeeeeeeef,"some people just love it")

... doing encoding ...

values1Encoded = 0x01 02 cafe 01 19 6e6f74207265616c6c79206120636166652c2069732069743f
values2Encoded = 0x01 08 beeeeeeeeeeeeeef 01 18 736f6d652070656f706c65206a757374206c6f7665206974

/// No errors as we know the length! 
/// And it only takes in most cases `2 * tuple.countOfNestedTypes` bytes more per 1 tuple
/// Where `countOfNestedTypes` is the number of types you declare within parentheses `()`.
decodeLsp2Values(type, values1Encoded)
decodeLsp2Values(type, values2Encoded)

[CJ42]

One thing mentioned by @frozeman is that for certain schema, like when valueType is a tuple with two bytes inside as (bytes,bytes).

In such case, the valueContent, should tell. but some combinations are not automatically decodable,