Allow entries creation with start date == end date of another existing entry

[enriquezrene]

As a user, I want to register my hours in an ordered way.
For example, I have these entries:

start_time: 10:00 end_time: 11:00
start_time: 11:01 end_time: 12:00
start_time: 12:01 end_time: 13:00

I would like to be able to have the entries with the following information:
start_time: 10:00 end_time: 11:00
start_time: 11:00 end_time: 12:00
start_time: 12:00 end_time: 13:00

From a technical perspective, this can be solved by playing a little bit with the seconds used. For example, we may set the start_time seconds equal to the end_time seconds + 1 if the entry is being created on the same day, hour, and minute. In this way, we can have the following data stored:

start_time: 10:00:59 end_time: 11:00:14
start_time: 11:00:15 end_time: 12:00:34
start_time: 12:00:35 end_time: 13:00:01

In this way, times are not going to overlap at all and they all are one next to each other.