title: Add a column value with the other date time column at minutes level in pandas
body: <p>I have a data frame as shown below </p>
  
  <pre><code>ID      ideal_appt_time            service_time
  1       2020-01-06 09:00:00        22
  2       2020-01-06 09:30:00        15
  1       2020-01-08 14:00:00        42
  2       2020-01-12 01:30:00        5
  </code></pre>
  
  <p>I would like to add service time in terms of minutes with ideal_appt_time and create new column called finish.</p>
  
  <p>Expected Output:</p>
  
  <pre><code>ID      ideal_appt_time            service_time       finish
  1       2020-01-06 09:00:00        22                 2020-01-06 09:22:00
  2       2020-01-06 09:30:00        15                 2020-01-06 09:45:00
  1       2020-01-08 14:00:00        42                 2020-01-08 14:42:00
  2       2020-01-12 01:30:00        35                 2020-01-12 02:05:00
  </code></pre>