feat: support go normal struct

[earlgray283]

No description provided.

[Copilot]

Pull Request Overview

This PR adds support for generating Go normal structs using a new "structs" generator by introducing new testdata, templates, and generator implementation.

• Introduces test fixtures for structs in both value-modifier and math/context based scenarios.
• Adds new templates (structs.go.tmpl, structs_common.go.tmpl) and generator implementation in internal/gen/structs.
• Updates fixgen_test.go to include the "structs" generator alongside yo and ent.

Reviewed Changes

Copilot reviewed 28 out of 31 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
test/structs/test/testdata-value-modifier/*.go	Adds test fixtures for value modifiers for normal structs.
test/structs/test/testdata-math-v1/*.go	Adds new test cases for math-based generation of normal structs.
test/structs/test/testdata-context/*.go	Adds context-aware test cases for normal structs.
test/structs/test/models/*.go	Provides model definitions for the new structs.
test/fixgen_test.go	Updates test runner to include the new "structs" generator.
internal/templates/templates.go	Registers new templates for structs generation.
internal/gen/util.go	Adjusts directory reading functions.
internal/gen/structs/structs.go	Implements the new structs generator.
internal/gen/generator.go	Enhances error reporting for file formatting.

Files not reviewed (3)

• internal/templates/structs.go.tmpl: Language not supported
• internal/templates/structs_common.go.tmpl: Language not supported
• test/structs/test/go.mod: Language not supported

Comments suppressed due to low confidence (1)

test/structs/test/testdata-math-v1/goldie-user.go:17

• Random ID generation here uses rand.Int63() while in similar contexts (e.g., in testdata-context) rand.Int64() is used; consider unifying the random ID function usage across tests for consistency.

ID:        rand.Int63(),

[Copilot]

The use of rand.Int64() here differs from other test files; standardizing the random ID generation method may reduce potential inconsistencies in tests.

Suggested change

	ID: rand.Int64(),
	ID: rand.New(rand.NewSource(time.Now().UnixNano())).Int63(),