feat: add SRC-16 Typed Structured Data

[CatspersCoffee]

Type of change

• New Standard (SRC16)
• Documentation
• Example Implementations.

Changes

The following changes have been made:

• Added SRC-16 standard for typed structured data hashing and signing.
• Implemented core encoding functions for atomic, dynamic and reference types.
• Added domain separator logic for cross-protocol signature safety.
• Created comprehensive test suite for encoders (see: tests ).
• Added example implementation with Mail struct for both SRC16Domain (Fuel) and EIP712Domain (Ethereum).
• Included documentation on backwards compatability.

Notes

• This standard enhances the Fuel ecosystem by providing a consistent way to handle structured data signing.
• Compatible with existing EVM wallet infrastructure through domain type flexibility.
• Designed to be extensible for future data types.
• Test coverage includes both single value, dynamic array and fixed array encoding.

Related Issues

Closes #

Checklist

• I have linked to any relevant issues.
• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation where relevant (API docs, the reference, and the Sway book).
  • If my change requires substantial documentation changes, I have requested support from the DevRel team
• I have added tests that prove my fix is effective or that my feature works.
• I have added the necessary New Feature labels where relevant.
• I have done my best to ensure that my PR adheres to the Fuel Labs Code Review Standards.
• I have requested a review from the relevant team or maintainers.
• I have updated the changelog to reflect the changes on this PR.

[fuel-cla-bot]

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[fuel-cla-bot]

Thanks for the contribution! Before we can merge this, we need @CatspersCoffee to sign the Fuel Labs Contributor License Agreement.

[SwayStar123]

Just giving you a heads up, we will be reviewing this standard in the following days, but Fuel is enacting a code freeze around christmas as many contributors will be on vacation etc. So this will likely not be merged until January as the earliest.

[bitzoic]

This is amazing!

Just a few questions, primarily surrounding whether the existing encoder and hashing functionality in the std-lib and core are sufficent/can be integrated or if we need to introduce new traits and structs.

I'm also curious on how handling Fuel specific types would work. We've made the distinct choice to separate the Address and ContractId types as well as have AssetId.

[SwayStar123]

I suggest changing the pseudocode to follow sway code formatting guidelines, as this is specifically a Sway standard, but it is fine as it is aswell.

[K1-R1]

Looking good to me; happy to approve once above comments are addressed and CI is passing

[CatspersCoffee]

I suggest changing the pseudocode to follow sway code formatting guidelines, as this is specifically a Sway standard, but it is fine as it is aswell.

apart from the rust tags in the docs, could you point me to fiels where I have not used Sway pseudocode in examples? I may be missing something

[SwayStar123]

I suggest changing the pseudocode to follow sway code formatting guidelines, as this is specifically a Sway standard, but it is fine as it is aswell.

apart from the rust tags in the docs, could you point me to fiels where I have not used Sway pseudocode in examples? I may be missing something

I was referencing the definition of the functions
under
### Definition of hashStruct

ie hashStruct -> hash_struct etc.

Also the CI is failing, you need to fix those errors or else this PR cannot be merged