Add and enforce validation struct tags for existing and future struct fields

[thep2p]

Problem

According to CLAUDE.md, the project uses github.com/go-playground/validator/v10 for struct validation. However, several public structs currently lack validation tags, which can lead to runtime panics when invalid instances are created.

Current Issues

1. BootstrapEntry struct (bootstrap/bootstrap.go:23-26) lacks validation tags:

   type BootstrapEntry struct {
       Identity    model.Identity
       LookupTable core.MutableLookupTable
   }

   Users can create invalid BootstrapEntry instances with nil lookup tables, leading to potential panics at runtime.

2. Missing validation enforcement - No systematic way to ensure new structs include appropriate validation tags

Impact

• Runtime safety: Without validation tags, invalid structs can be created and cause panics
• Developer experience: Errors occur at runtime instead of at construction time
• Code quality: Inconsistent validation patterns across the codebase

Proposed Solution

1. Add Validation Tags to Existing Structs

Identify and add validation tags to all public structs that should be validated:

type BootstrapEntry struct {
    Identity    model.Identity              `validate:"required"`
    LookupTable core.MutableLookupTable     `validate:"required"`
}

Note: If model.Identity and core.MutableLookupTable are value types (not pointers), document why validation isn't needed or if zero-value is acceptable.

2. Create Validation Guidelines

Add a section to CLAUDE.md or create a CONTRIBUTING.md with guidelines:

• When to add validation tags
• How to validate structs (call validator in constructors)
• Examples of common validation patterns
• Exception cases (e.g., internal-only structs, value types where zero-value is valid)

3. Potential Linting/Static Analysis

Consider adding a linter rule or custom tool to:

• Detect public structs without validation tags
• Verify validation is called in constructors
• Flag potential validation issues in code review

Acceptance Criteria

• Audit all public structs and identify which need validation tags
• Add validation tags to existing structs (e.g., BootstrapEntry)
• Update documentation with validation guidelines
• Add validation calls in constructors where appropriate
• Consider adding linter rule or static analysis tool
• Add tests to verify validation works correctly

Examples of Structs to Audit

• bootstrap.BootstrapEntry
• Network layer message types
• Identity and addressing types
• Configuration structs
• Any public API types that could be constructed by users

References

• Project uses github.com/go-playground/validator/v10
• Mentioned in CLAUDE.md as a project dependency
• Identified in PR Refactor bootstrap to return BootstrapEntry instead of SkipGraphNode #51 code review as a missing feature

Priority

Cosmetic / Low Priority - This is a code quality improvement that enhances safety but doesn't block current functionality. Can be addressed incrementally.