feat: add comprehensive input validation for token operations (#1534)

[NETIZEN-11]

Summary

Implements comprehensive input validation for token operations (Issue, Transfer, Redeem) to ensure data integrity,
security, and consistency.

Changes

New Validation Package (token/services/validation/)

• ValidateAmount() - validates token amounts (non-zero, within max limit)
• ValidateAddress() - validates recipient addresses (non-empty, max 256 bytes)
• ValidateTokenType() - validates token types (non-empty)
• ValidateMetadata() - validates metadata fields (key presence, 10KB size limit)
• ValidateTransferValues() - validates transfer values and owners arrays
• ValidateRedeemValue() - validates redeem values

Error Types with Codes

• InvalidAmountError
• InvalidAddressError
• InvalidMetadataError
• InvalidTokenTypeError
• ValidationError

Enhanced token/request.go

Issue() - Added:

• Metadata size validation (10KB limit per value)

Transfer() - Added:

• Token type validation (non-empty)
• Index-specific zero value error messages
• Owners/values length mismatch validation
• All owners must be defined validation
• Metadata size validation

Redeem() - Added:

• Token type validation (non-empty)
• Value zero validation
• Metadata size validation

validateMetadata() - New helper function for metadata validation

Test Results

All unit tests pass:
PASS ok github.com/hyperledger-labs/fabric-token-sdk/token/services/validation
PASS ok github.com/hyperledger-labs/fabric-token-sdk/token

Acceptance Criteria Met

• Validate token amounts (non-negative, within limits)
• Sanitize and validate recipient addresses
• Validate metadata fields (type, length, format)
• Provide clear and specific error messages for validation failures
• Add unit tests for all validation scenarios
• Custom exceptions for validation failures

Related Issue

Fixes #1534

Test plan

• Run unit tests: go test ./token/services/validation/...
• Run request tests: go test ./token -run TestRequest
• Build verification: go build ./token/...

[NETIZEN-11]

@adecaro Would love a review on this. Thanks!

[adecaro]

Hi @NETIZEN-11 , sorry for this very late reply. I'm reviewing it now 🙏

[adecaro]

Hi @NETIZEN-11 , I'm not sure the PR achieves the goals stated in the Issue. There are many validation functions but they are not used.
Some more general comments:

• Typed errors are more than enough, no need for error codes.
• When possible, use always constants instead of magic values.

Thanks for the effort 🙏