Add First and Last name to the user identity object

[rdimitrov]

Summary

The following PR adds First and Last name to the user identity object and to the ListRoleAssignments response.

Fixes #3831

Change Type

Mark the type of change your PR introduces:

• Bug fix (resolves an issue without affecting existing features)
• Feature (adds new functionality without breaking changes)
• Breaking change (may impact existing functionalities or require documentation updates)
• Documentation (updates or additions to documentation)
• Refactoring or test improvements (no bug fixes or new functionality)

Testing

Outline how the changes were tested, including steps to reproduce and any relevant configurations.
Attach screenshots if helpful.

Review Checklist:

• Reviewed my own code for quality and clarity.
• Added comments to complex or tricky code sections.
• Updated any affected documentation.
• Included tests that validate the fix or feature.
• Checked that related changes are merged.

[coveralls]

coverage: 52.141% (+0.01%) from 52.128%
when pulling e4b684a on add-first-last-name
into 9fbf426 on main.

[evankanderson]

I think you can take advantage of proto3's empty-field behavior and simplify:

Suggested change

	ret := &auth.Identity{
	UserID: *user.Id,
	HumanName: *user.Username,
	Provider: k,
	}
	// If the user has a first and last name, return them too
	if user.FirstName != nil {
	ret.FirstName = *user.FirstName
	}
	if user.LastName != nil {
	ret.LastName = *user.LastName
	}
	return ret
	ret := &auth.Identity{
	UserID: *user.Id,
	HumanName: *user.Username,
	Provider: k,
	FirstName: *user.FirstName,
	LastName: *user.LastName,
	}
	return ret

[rdimitrov]

Actually I did try it like that but for users where this was missing, it was failing because of the nil reference.