Generate a joining offer letter for {applicant_name} who has been selected for the position of {job_title} at {app_name}. Customize the letter by filling in the appropriate details and placeholders enclosed in {}. Please structure the letter to include the mentioned variables in their respective sections. Sign off the letter with the company name.Variables:{applicant_name},{app_name},{job_title},{start_date},{workplace_location},{days_of_week},{salary},{salary_type},{offer_expiration_date} and  letter must be descriptive with eficient information