fix: panic username not set for token

[Tinyblargon]

Fix issue where we parsed the raw username when using an API token, causing a panic.

[Copilot]

Pull Request Overview

This PR fixes a panic that occurs when parsing usernames for API token authentication in the Proxmox client. The issue was caused by attempting to parse a raw username when using an API token, which has a different format than regular usernames.

• Replaces strings.SplitN with strings.IndexRune for more robust parsing
• Adds conditional logic to handle both username and API token scenarios
• Extracts user and realm information from API tokens when username is not set

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[Copilot]

If '@' is not found in c.Username, IndexRune returns -1, which will cause a panic when used for slicing. Add a check to ensure index >= 0 before slicing.

Suggested change

	user = UserID{Name: c.Username[:index], Realm: c.Username[index+1:]}
	if index >= 0 {
	user = UserID{Name: c.Username[:index], Realm: c.Username[index+1:]}
	} else {
	// Handle missing '@' gracefully; fallback to entire username as Name, empty Realm
	user = UserID{Name: c.Username, Realm: ""}
	}

[Copilot]

If '@' or '!' characters are not found in the token, IndexRune returns -1, which will cause panics during slicing operations. Add bounds checking for both indexAt and indexEx before using them for slicing.

Suggested change

	indexEx := strings.IndexRune(token[indexAt+1:], '!')
	user = UserID{Name: token[:indexAt], Realm: token[indexAt+1 : indexAt+indexEx+1]}
	if indexAt == -1 {
	user = UserID{Name: "", Realm: ""}
	} else {
	indexEx := strings.IndexRune(token[indexAt+1:], '!')
	if indexEx == -1 {
	user = UserID{Name: "", Realm: ""}
	} else {
	user = UserID{Name: token[:indexAt], Realm: token[indexAt+1 : indexAt+indexEx+1]}
	}
	}