fix(client): build the User-Agent from the assembly version - #22

Converting null literal or possible null value to non-nullable type.

Non-nullable property 'ResponseContent' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the property as nullable.

Converting null literal or possible null value to non-nullable type.

Non-nullable property 'ResponseContent' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the property as nullable.