Add createERC20TokenPeriodTransferTerms for @metamask/delegation-core

[jeffsmale90]

📝 Description

Adds terms builder to @metamask/delegation-core for the ERC20 Token Periodic Transfer caveat builder.

🔄 What Changed?

List the specific changes made:

• Adds createERC20TokenPeriodTransferTerms function to @metamask/delegation-core
• Updates erc20PeriodTransferBuilder to consume this new terms builder
• Simplifies createERC20StreamingTerms, by using the prefixed token address, instead of stripping the prefix, and re-adding later.

🚀 Why?

This caveat is now used within the readable permissions gator snaps, so building the terms must be performed within @metamask/delegation-core, so as to not require @metamask/delegation-toolkit dependency within the snaps.

🧪 How to Test?

Existing unit tests for erc20PeriodTransferBuilder, and e2e integration tests cover this functionality, as well as new unit tests covering the new createERC20TokenPeriodTransferTerms function.

⚠️ Breaking Changes

List any breaking changes:

• No breaking changes
• Breaking changes (describe below):

📋 Checklist

Check off completed items:

• Code follows the project's coding standards
• Self-review completed
• Documentation updated (if needed)
• Tests added/updated
• Changelog updated (if needed)
• All CI checks pass

🔗 Related Issues

Link to related issues:
Closes #
Related to #

📚 Additional Notes

Any additional information, concerns, or context:

[Copilot]

Pull Request Overview

Adds a new terms builder for periodic ERC20 token transfers in @metamask/delegation-core and updates related builders to use prefixed addresses.

• Introduce createERC20TokenPeriodTransferTerms in the core package.
• Update erc20PeriodTransferBuilder in the toolkit to call the new core function.
• Simplify ERC20 streaming builder to include the full 0x-prefixed address.
• Export and document the new terms builder in the core README.

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
packages/delegation-toolkit/src/caveatBuilder/erc20PeriodTransferBuilder.ts	Replace manual term concatenation and validation with core’s createERC20TokenPeriodTransferTerms.
packages/delegation-core/src/index.ts	Export createERC20TokenPeriodTransferTerms.
packages/delegation-core/src/caveats/index.ts	Add export for the new caveat terms builder.
packages/delegation-core/src/caveats/erc20TokenPeriodTransfer.ts	Implement new terms builder with validation and encoding logic.
packages/delegation-core/src/caveats/erc20Streaming.ts	Rename tokenAddressHex to prefixedTokenAddressHex and include full 0x prefix.
packages/delegation-core/README.md	Document the new createERC20TokenPeriodTransferTerms API.

Comments suppressed due to low confidence (2)

packages/delegation-core/README.md:199

• The documentation states the terms are 128 bytes (32 bytes per parameter), but the implementation uses a 20-byte address plus three 32-byte values (116 bytes total). Please update the description to match the actual encoding or pad the address to 32 bytes.

**Returns:** `Hex | Uint8Array` - 128-byte encoded terms (32 bytes per parameter)

packages/delegation-core/src/caveats/erc20Streaming.ts:74

• [nitpick] Consider renaming prefixedTokenAddressHex to a more concise or descriptive name such as tokenAddressWithPrefix, or revert to tokenAddressHex if the prefixing behavior is consistent across builders.

  let prefixedTokenAddressHex: string;