Improve user agent handling in login classes

[LeMyst]

Updated the construction of the 'User-Agent' header in both Login and Clientlogin classes to use a fallback to config['USER_AGENT'] if user_agent is not provided, ensuring a valid user agent string is always set.

[Copilot]

Pull Request Overview

This PR updates the User-Agent header handling in the Login and Clientlogin classes to add fallback logic that uses the global config's USER_AGENT value when no explicit user agent is provided. However, the implementation introduces code duplication.

• The fallback logic user_agent or (str(config['USER_AGENT']) if config['USER_AGENT'] is not None else None) is applied twice in each class
• The duplication occurs both where the variable is first assigned and again when passed to get_user_agent()

[Copilot]

The fallback logic user_agent or (str(config['USER_AGENT']) if config['USER_AGENT'] is not None else None) is redundant here. The variable user_agent was already resolved with the same fallback logic on line 215, so this line can be simplified to just get_user_agent(user_agent).

Suggested change

	'User-Agent': get_user_agent(user_agent or (str(config['USER_AGENT']) if config['USER_AGENT'] is not None else None))
	'User-Agent': get_user_agent(user_agent)

[Copilot]

The fallback logic user_agent or (str(config['USER_AGENT']) if config['USER_AGENT'] is not None else None) is redundant here. The variable user_agent was already resolved with the same fallback logic on line 274, so this line can be simplified to just get_user_agent(user_agent).

Suggested change

	'User-Agent': get_user_agent(user_agent or (str(config['USER_AGENT']) if config['USER_AGENT'] is not None else None))
	'User-Agent': get_user_agent(user_agent)